Effect of reduced local lattice disorder on the magnetic properties of B-site substituted La0.8Sr0.2MnO3

Journal of Magnetism and Magnetic Materials 529 (2021) 167893

Available online 14 March 2021

0304-8853/© 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Effect of reduced local lattice disorder on the magnetic properties of B-site substituted La _0.8 Sr _0.2 MnO ₃

Sagar Ghorai

, Sergey A. Ivanov

, Ridha Skini

, Petter Str¨om

, Peter Svedlindh

aDepartment of Materials Science and Engineering, Uppsala University, Box 35, SE-751 03 Uppsala, Sweden

bSemenov Institute of Chemical Physics, Kosygina Street, 4, Moscow 119991, Russia

cApplied Nuclear Physics, Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden

A R T I C L E I N F O Keywords:

Griffiths phase Jahn-Teller effect Dimerons

Magnetocaloric effect Spin cluster state

A B S T R A C T

Disorder induced by chemical inhomogeneity and Jahn-Teller (JT) distortions is often observed in mixed valence perovskite manganites. The main reasons for the evolution of this disorder are connected with the cationic size differences and the ratio between JT active and non-JT active ions. The quenched disorder leads to a spin-cluster state above the magnetic transition temperature. The effect of Cu, a B-site substitution in the La0.8Sr0.2MnO3 compound, on the disordered phase has been addressed here. X-ray powder diffraction reveals rhombohedral (R- 3c) structures for both the parent and B-site substituted compound with negligible change of lattice volume. The chemical compositions of the two compounds were verified by ion beam analysis technique. With the change of electronic bandwidth, the magnetic phase transition temperature has been tuned towards room temperature (318 K), an important requirement for room temperature magnetic refrigeration. However, a small decrease of the isothermal entropy change was observed with Cu-substitution, related to the decrease of the saturation magnetization.

1. Introduction

Mixed valence perovskite manganite oxides (AxB1-xMnO3) have attained much attention owing to magnetic disorder driven by competing magnetic interactions and coupling between charge, spin, lattice and orbital degrees of freedom [1]. Mostly, they exhibit two types of exchange interactions; ferromagnetic (FM) double-exchange inter- action via Mn³⁺- O^2-- Mn⁴⁺ and antiferromagnetic (AFM) super- exchange interaction via Mn³⁺- O^2-- Mn³⁺ (or Mn⁴⁺- O^2-- Mn⁴⁺).

Depending on the Mn³⁺/Mn⁴⁺ratio there will be a varying degree of competing FM-AFM interactions. The competing interactions can cause magnetic disorder in manganites, which is often revealed by a Griffiths phase (GP) singularity [2]. In the original work of Griffiths [3], a randomly diluted Ising ferromagnetic system was considered with only a fraction of the lattice-sites occupied with nearest-neighbour interacting Ising spins. If the lattice system is considered as a state ψ, and lattice- sites with and without Ising spins are described as v(ψ) and s(ψ), respectively, then the probability of the lattice system can be written as, P(ψ) =P(v) + P(s) = 1

For an undiluted or homogeneous ferromagnetic system, P(s) = 0

[2–5]. For P(v) < 1,above a certain value (percolation threshold), long- range ferromagnetic order is complete at a probabilistic transition temperature TC(P(v)), which is less than the transition temperature of an undiluted system [3]. In case of P(v) < 1, ferromagnetic order begins to develop below the Griffiths temperature (TG) as finite size ferro- magnetically ordered spin-clusters. The temperature region between TG

and TC is defined as the GP-region [4]. Obviously, the width of the GP- region region depends on P(v), but in systems with competing FM and AFM interactions it will also depend on the relative amount and strength of these interactions. Thus, in perovskite manganites with competing exchange interactions, the Mn³⁺/Mn⁴⁺ratio can tune the width of the GP-region.

Previously, the evolution of the GP-region in manganites has been studied for different A-site substitutions [5–11,12]. However, in most cases A-site substitution introduces a change of lattice volume or even a change in crystal structure, which does not concur with the original model of Griffiths [3]. Thus, A-site substitution often introduces addi- tional changes in the system that can mask the effect of disorder on the evolution of the GP phase. There are only a few reports, [2,13] which describe the dependence of the GP phase on B-site substitution and the reason for an increasing or decreasing width of the GP region in B-site

* Corresponding author.

E-mail address: sagar.ghorai@angstrom.uu.se (S. Ghorai).

Contents lists available at ScienceDirect

Journal of Magnetism and Magnetic Materials

journal homepage: www.elsevier.com/locate/jmmm

https://doi.org/10.1016/j.jmmm.2021.167893

Received 17 November 2020; Received in revised form 29 January 2021; Accepted 23 February 2021

substituted manganites is not clear. The strength and the relative amount of FM and AFM interactions between B-site atoms together with local lattice distortions due to Jahn-Teller active ions govern the for- mation and evolution of ferromagnetic clusters above TC.

In this work we have substituted the B-site of La_0.8Sr_0.2MnO₃ with magnetic Cu-atoms. With the support of electronic structure analysis, we have characterized the magnetic interactions between B-site atoms and their effect on the formation of the GP phase. As manganites can be tuned to act as a magnetic refrigerant near room temperature, [14,15]

the effect of B-site substitution on the magnetocaloric effect has also been studied in this work. A comparatively high value of isothermal entropy change (see Table 2) over a wide temperature span, makes this substitution interesting for room temperature magnetic refrigeration applications.

2. Experimental details

The La_0.8Sr_0.2MnO₃ (LS) and La_0.8Sr_0.2Mn_0.9Cu_0.1O₃ (LSC) com- pounds were prepared by solid-state reaction. Stoichiometric amounts of La2O3, Sr2O3, MnCO3 and CuO powders were mixed together and cal- cinated at 1473 K for 24 h in Ar-atmosphere. The samples were char- acterized using X-ray powder diffraction (XRPD) at 295 K by using a Bruker D8 Advance diffractometer with Cu-Kα radiation and an angle step size of 0.021^◦. The elemental analysis of the samples was performed by time-of-flight elastic recoil detection analysis (ToF-ERDA) [16] with 36 MeV ¹²⁷I⁸⁺. The incidence angle of the ion-beam was 23^◦±1^◦with respect to the sample surface, and recoils were detected at 45^◦. Simul- taneous Rutherford backscattering spectrometry (RBS) and particle induced X-ray emission (PIXE) with a 2 MeV ⁴He⁺beam and detectors at 170^◦ (RBS) and 135^◦ (PIXE) were also applied. X-ray photoelectron spectroscopy (XPS) was used to analyse the oxidation states and valence band spectra of the samples. The XPS spectra were collected by using a

“PHI Quantera II” system with an Al-Kα X-ray source and a hemi- spherical electron energy analyser having a pass energy of 26.00 eV. Pre- sputtering with Ar-ions of 200 eV for 30 s was done on the samples before collecting the XPS spectra in order to remove surface impurities without affecting the sample’s properties. A Quantum Design MPMS XL system was used to measure the magnetic properties in the temperature range from 390 K to 5 K with a maximum field of 5 T.

3. Results and discussion 3.1. Crystal structure

The analysis of the XRPD spectra (Fig. 1(a) and (b)) with the Fullprof

program [17] reveals a single phase rhombohedral structure for the two compounds. During XRPD analysis several structural models, ortho- rhombic, monoclinic, rhombohedral, etc. were fitted and the best fit of the structural model was observed for the rhombohedral structure with a space group R-3c. The structural parameters are listed in Table 1. The absence extra peaks and similar lattice parameters in the Cu-substituted compound, confirm that the Cu-atoms have substituted the Mn-site (6e- site) of the lattice.

The crystal structure can also be described with the Goldschmidt tolerance factor [18] (tG= ̅̅^rA+rO

√2

(rB+rO), where rA, rB and rO are the ionic radii of A, B and oxygen ions, respectively). For the LS and LSC com- pounds the values of tG are very close (0.921 and 0.923, respectively) even if the mixed valence of Cu (+2 and + 3 oxidation states) is considered (from XPS analysis, described later). The tG values are calculated using the ionic radii (calculated by R. D. Shannon[19]) of the La⁺³, Sr²⁺, Mn⁺³, Mn⁺⁴, Cu⁺², Cu⁺³ and O^-2 ions as 1.216, 1.31, 0.645, 0.53, 0.73, 0.54 and 1.4 Å, respectively. The lattice distortion in the compounds can be understood more clearly in terms of the deviation from cubic symmetry defined as, q =^c/2 ̅̅

√3 a/ ̅̅

√2 [20,21]. The almost same values of q for the two compounds are listed in Table 1. This minimal difference in the crystal structures of the two compounds provides the opportunity to study the effect of disorder and GP-evolution without influence from a crystal structure change as mentioned in the introduction.

3.2. Electronic structure

The magnetic properties of the LS and LSC compounds are strongly dependent on the amount of Mn and Cu mixed valence states. The ex- change interactions in the compounds, e.g. ferromagnetic Mn⁺³- O^-2- Mn⁺⁴, antiferromagnetic Mn⁺³- O^-2- Mn⁺³ (or Mn⁺⁴- O^-2- Mn⁺⁴), anti- ferromagnetic Mn⁺³- O^-2- Cu⁺² (for LSC compound), depend on the relative amounts of the different oxidation states of the magnetic Mn and Cu-ions. In order to, carefully investigate the oxidation states of these two elements, XPS analysis has been performed. Mainly, two oxidation states for both Mn (+3 and + 4) and Cu (+2 and + 3) were observed from the XPS core level spectra of Mn 2p (Fig. 2(a)) and Cu 2p (Fig. 2(b)) states. Owing to the spin orbital splitting of Mn 2p3/2 and Mn 2p1/2 states two distinct peaks near ~ 641 eV and ~ 653 eV were observed for the both compounds (cf. Fig. 2(a)). However, in the LSC compound, a broad feature near ~ 647 eV was also observed and this feature is not a satellite peak for the Mn⁺² state [23]. M.S. Kim et al. [24] identified this feature as a mixed state of Mn³⁺ and Mn⁴⁺. They also observed that with increasing Cu-substitution in the La0.7Sr0.3MnO3 system this mixed state feature shifts towards higher binding energy as a result of an increasing relative amount of Mn⁴⁺ ions in the compound. Thus, for the LSC compound the increased amount of Mn⁴⁺-ions could explain the observation of this broad feature in the Mn 2p core level spectrum.

However, owing to the presence of this ~ 647 eV feature, any type of quantitative analysis of the Mn 2p peak is difficult. The Mn 3s spectra is

Fig. 1. X-Ray powder diffraction patterns of (a) LS and (b) LSC samples.

Table 1 Structural results.

Compound LS LSC

Space Group R-3c R-3c

Lattice parameters (Å) a 5.52240(4) 5.52280(4)

c 13.33689

(12) 13.3630

(11)

q 0.986 0.988

Mn-O Bond lengths (Å) 1.9642(7) 1.9664(7)

Mn-O-Mn Bond angle (^◦) 163.90(16) 162.99(17)

Rietveld Refinement Parameters[22] for

XRPD RP 7.32 6.19

RWP 9.77 8.31

RB 5.27 4.90

more precise for identification of the Mn oxidation states. The Mn 3s spectra have two distinct peaks originating from the parallel and anti- parallel coupling between the Mn 3s core holes and the Mn 3d electrons [25]. There is a linear relationship between the magnitude of the Mn 3s exchange splitting (ΔE) and the spin of the 3d electrons; ΔE∝(2S +1) [26]. As references for the Mn⁺³ and Mn⁺⁴ states, the exchange splitting of the Mn2O3 and MnO2 compounds have been considered (Fig. 2(C)).

Also, Beyreuther et al. derived a simple relationship between the Mn- valance state (v) and ΔE, as,

v = 9.67 − 1.27 × ΔE (1)

Using the ΔE values of the reference samples in Eq. (1) and comparing it with the value of LS compound, the value of Mn³⁺/Mn⁴⁺

for the LS compound was calculated as 2.91(9).

However, for the LSC compound the Mn 3s state is coupled with the Cu 3p state, thus the above-mentioned quantitative analysis cannot be performed for the LSC compound. For the determination of the Mn valence state in the LSC compound, the total chemical formula has been considered, as,

La⁺³_0.8Sr⁺²_0.2Mn⁺³_x Mn⁺⁴_{(1− p− x)}Cu⁺²_y Cu⁺³_{(p− y)}O⁻₃ ²

where x and y correspond to the amount of Mn³⁺and Cu²⁺ ions, respectively, and p to the total amount of Cu ions. From charge neutrality (neglecting any oxygen deficiency) we have,

x + y + p = 0.8 (2)

Here, p is 0 and 0.1 for the LS and LSC compounds, respectively.

From the fitting of the Cu 2p3/2 peak (Fig. 2(b)) of the LSC compound, the value of y is calculated as 0.075(25). Using the value y in Equation (2), the value of Mn³⁺/Mn⁴⁺for the LSC compound was calculated as 2.3(3). Thus, with Cu-substitution, the Mn³⁺/Mn⁴⁺ratio decreases from 2.91(9) to 2.3(3), indicating an increased amount of Mn⁴⁺-ions in the LSC compound. Considering the error in the XPS results, we have to keep in mind that the calculated values are only approximate estimates, made to understand the increment of Mn⁴⁺-ions with Cu-substitution. As we will see later (in the magnetic part), the increment of Mn⁴⁺ions, is Table 2

Chemical and magnetic results.

Compound LS LSC

Atomic % from TOF-ERDA Mn 22.2(12) 20.6(11)

Cu – 2.0(2)

O 59.3(33) 58.3(31)

TC(K) 330(2) 318(2)

MS(Am²/kg) 90.99 81.40

-ΔS^maxM (J/kg-K) at 5T 5.18 4.53

RCP (J/kg) at 5T 245 230

GP% μ₀H = 0.01T 15% –

μ₀H = 0.05T 13% –

μ₀H = 0.1T 12% –

Fig. 2. XPS spectra of (a) Mn2p state of LS and LSC compounds, (b) Cu-2p state of the LSC-compound, (c) Mn3s states of LS-and reference compounds and (d) valence band spectra of LS and LSC compounds.

directly proportional to the decrease of the local lattice distortion caused by the Jahn-Teller effect in the compound.

The valence band spectra for the LS and LSC compounds are shown in Fig. 2(d). In general, the valence band spectrum of a perovskite manganite has four binding energy contributions A, B, C and D, as indicated in Fig. 2(d), where A corresponds to the O 2p-Mn 3d t2g hy- bridized state, B to the nonbonding O 2p state, C to the Mn 3d t2g state and D to the Mn 3d eg state [26–29]. In the LSC compound there is a contribution from the Cu 3d orbital in the binding energy range 2–4 eV [24], which is revealed by the increase of density of states for these energies. Also, from theoretical calculations it is known that only the eg

state of Cu 3d will contribute to the density of states below the Fermi- level [24], which is an indication of the strong coupling between the Mn 3d t2g and Cu 3d eg orbitals and the nature of this coupling (FM or AFM) will to some extent control the magnetic properties of the LSC compound.

3.3. Ion beam analysis

Raw ToF-ERDA data are shown in Fig. 3(a) and (b). In addition to the expected elemental contents, impurity signals due to approximately 0.5–1.5 at. % of H and C were detected on both samples. For the LSC sample, a faint signal due to Si or Al contamination was also detected,

part of which may be attributed to the beam grazing the Al sample holder. Depth profiling of the ToF-ERDA data with Potku [30], including all detected signals, and integration from depth 1.5 × 10¹⁷ at/cm² to 1.5

×10¹⁸ at/cm² yielded an estimation of the sample composition. The obtained RBS data indicated concentration gradients for La and Sr near the sample surface, making fitting of the relative concentrations ambiguous. Further, a heavy impurity at concentration ≲ 0.2 at. % was detected, identified as Pb from the PIXE spectra shown in Fig. 3(c).

For Mn, the number of counts in the region of the ToF-ERDA spec- trum from which data was considered is between 1000 and 2500 for the two samples, yielding a relative statistical uncertainty of 2–3%. The corresponding number for Sr and Cu is 4–5%, while background counts amount to approximately 5–8% of the collected data from these ele- ments. Further, an uncertainty in relative detection efficiency between Mn or Cu and O contributes an error up to 5%. The atomic fractions of Mn, O and Cu obtained from ToF-ERDA are listed in Table 2 and they are comparable with the expected values. Varying the integration depth over a range up to a maximum of 2 × 10¹⁸ at/cm², to ascertain the effect of near-surface concentration gradients, yields a variation of the Mn, O and Cu concentrations within the given error margins.

Fig. 3. Raw ToF-ERDA data for samples (a) LS and (b) LSC. (c) PIXE spectra obtained on LS and LSC samples, with detected elements indicated. The peaks observed between the Pb Mα-line at 2.35 keV and the set of L-lines from La and Pb are a combination of other Pb M-lines and escape peaks due to excitations in the Si drift detector.

3.4. Magnetic and magnetocaloric properties

A second order paramagnetic to ferromagnetic (PM-FM) transition was observed (using Banerjee Criterion[31–34]) in both compounds.

However, the transition temperature (TC) decreased with Cu- substitution (from 330 K to 318 K, cf. Fig. 4(a)). Since double- exchange interaction is responsible for the ferromagnetism in the two compounds, one expects that TC should be governed by the electronic bandwidth (W),[35] which is defined as,

W∝cos(1/2(π− 〈Mn − O − Mn〉))

d^3.5_{Mn− O} (3)

where 〈Mn − O − Mn〉 and dMn− Oare the bond angle and bond length, respectively. From Table 1, a decrease of W is observed with Cu- substitution, which is in accord with the observed decrease of TC, and in good agreement with previously reported results for manganites.[35]

Moreover, Cu-substitution introduces a new AFM, Mn³⁺–O^2--Cu²⁺

superexchange interaction[36] in the compound and also reduces the saturation magnetization (cf. Fig. 4(b)).

A Griffiths phase like behaviour was observed in the LS compound (Fig. 4(c)), implying that ferromagnetically ordered clusters are formed in the paramagnetic region below the Griffiths temperature TG. The GP, which is suppressed in the LSC compound, can be characterized by the temperature dependence of the magnetic susceptibility according to[2]

χ⁻¹∝(T − T_C^R)^{1− λ} (4)

where 0 ≤ λ < 1 and T^R_C is the critical temperature where the suscepti- bility tends to diverge. The different transition temperatures TC, TG, T^R_C are determined following the method discussed by A.K. Pramanik et al.

[2] In Fig. 4(c), the red line indicates the fitting of the inverse suscep- tibility of the LS compound below TG with Equation (4). The

temperature range of the GP is described as,[2]

GP% =TG− TC

TC

×100 (5)

Both λ and GP% decrease with increasing magnetic field; λ (GP%) was found to be 0.29, 0.24 and 0.12 (15%, 13% and 12%) for applied fields of 0.01 T, 0.05 T and 0.1 T, respectively in the LS compound.

In the La(1-x)SrxMnO3 system, Jahn-Teller (JT) distortions have been identified as the reason for the appearance of the GP[7]. JT distortions exist for Mn³⁺ions, as there is only one electron in a degenerate eg-state and to reduce its energy there will be a geometrical distortion along one of the fourfold axes. For the Mn⁴⁺ion there is no JT distortion since no electron occupies the eg-state. Similarly, Cu²⁺ions exhibit a JT distor- tion, while Cu³⁺ions don’t. From the balance of valence charges, Cu²⁺

substitution will increase the amount of Mn⁴⁺ions and decrease the amount of Mn³⁺ions. The substitution is straight forward for Cu³⁺, it only replaces Mn³⁺ions. As a combined effect of Cu²⁺and Cu³⁺sub- stitutions, the ratio of JT ions (Mn³⁺and Cu²⁺) to non-JT ions (Mn⁴⁺

and Cu³⁺) will decrease. A direct evidence of this argument is observed in the XPS analysis.

Two types of JT distortions have been identified; pairs of weakly distorted Mn⁺³-Mn⁺⁴ ions, each pair sharing an electron-hole pair, and isolated Mn⁺³ ions exhibiting considerably larger lattice distortions [37]. The energy barrier for activated hopping of charge carriers will be large for isolated Mn⁺³ ions, while the barrier will be much reduced for pairs of Mn⁺³-Mn⁺⁴ ions, referred to as dimers by Kumar et al.[38] and dimerons by Downward et al. [39] Dimerons form at some temperature above TC (here related to TG), where there is a deviation from the Curie- Weiss law in the temperature dependent susceptibility plot, and favour ferromagnetic double-exchange interaction via mobile charge carriers.

As the magnetic transition temperature is approached, dimerons will form small clusters and the evolution of these clusters is similar to

Fig. 4. (a) Low-field magnetization versus temperature and (b) magnetization versus magnetic field at 5 K. Temperature dependence of (c) inverse susceptibility and (d) isothermal entropy change for LS and LSC samples. Black (red) data-points give the result for LS (LSC) compound.

diffusion limited aggregation [39]. The formation of spin clusters de- pends on the amount of local lattice distortions and the availability of electron hole-pairs in the compound. The overall decrease of JT-active ions in the Cu substituted compound restricts the formation of spin clusters, implying that the compound from a magnetic perspective be- comes more homogeneous.

The magnetocaloric (MCE) properties have been characterized in terms of the isothermal entropy change using magnetometry. From Maxwell’s relation the isothermal entropy change (ΔSM) can be expressed as,[14]

ΔSM=μ₀

∫_Hf

Hi

(∂M

∂T )

H

dH (6)

where μ₀is the free-space permeability, Hi and Hf are the initial and final applied magnetic fields, respectively. Also, for real applications it is important to realise a sufficiently large effective temperature range in which a refrigeration process will work and the relative cooling power (RCP)[14] is a measure of this. The RCP is defined as,

RCP = − ΔS^max_M ×ΔTFWHM (7)

where − ΔS^max_M is the isothermal entropy change maximum and ΔTFWHM

is the full width at half maximum of the − ΔSM versus temperature curve. The field and temperature dependence of the isothermal entropy change for the LS and LSC compounds are shown in Fig. 4(d). The maximum value of isothermal entropy change was observed near TC for both compounds. At an applied field of 5 T, the entropy maximum and the RCP value decrease by 12.5% and 6%, respectively with 10% Cu- substitution in the B-site (see Table 2). This is also expected from the decrease of the saturation magnetization with Cu-substitution. Howev- er, Cu-substitution is still of value as it lowered the temperature where ΔS^max_M occurs towards room temperature.

4. Discussion

The effect of partial substitution of Mn with Cu in La0.8Sr0.2MnO3 on structural, electronic, chemical, magnetic and magnetocaloric proper- ties are described here. Rhombohedral (R-3c) structures with almost the same lattice parameters were observed for the two compounds, which allows for a purer investigation of how lattice distortion and competing magnetic interactions (arising from additional AFM interactions of type Mn⁺³-O^2--Cu⁺²) affect the evolution of a GP. From XPS analysis negli- gible amount of O-deficiency was observed for the two compounds, which is also important to avoid effect of anions on the valence charge of B-site magnetic ions. In the LS compound, the GP was observed due to local lattice distortions and aggregation of dimerons, associated with the JT-effect. This spin disordered phase is suppressed in the LSC compound owing to the decrease of the number of JT-active ions. In the LSC compound the ratio of JT/non-JT ions is 2.49, which is close to the value 2.33 observed for La0.7Sr0.3MnO3 compound for which there is also no GP-singularity [40]. However, the La0.7Sr0.3MnO3 compound has a higher TC (368.45 K), which can be explained by the reduction of the electronic bandwidth with Cu-substitution. Recently, A. Chanda et al.

[41] have reported a change of TC of ~ 50 K with a 10% Ga-substitution for Mn in the La0.6Sr0.4MnO3 compound. This change of TC is five times larger than the decrease of TC in this work, although in both cases there is a decrease of JT-active ions. Thus, the value of TC mostly depends on the electronic bandwidth, while the GP-disorder depends on the number of JT-active ions. The Cu-substitution plays two crucial roles, sup- pressing the disordered GP by reducing the number of JT-active ions and tuning the value of TC towards room temperature by decreasing the electronic bandwidth. Apart from this, a reasonable value of the relative cooling power and isothermal entropy change near room temperature make B-site substitution with Cu-ions interesting for solid state cooling devices.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The Swedish Foundation for Strategic Research (SSF, contract EM- 16-0039) supporting research on materials for energy applications is gratefully acknowledged. Infrastructural grants by VR-RFI (#2017- 00646_9) and SSF (contract RIF14-0053) supporting accelerator opera- tion are gratefully acknowledged. Financial support by FITC HF RAS through project No. 45.22 (grant AAAA18-118012390045-2) is grate- fully acknowledged.

References

[1] A. Moreo, S. Yunoki, E. Dagotto, Phase separation scenario for manganese oxides and related materials, Science (80-.). 283 (1999) 2034–2040. Doi: 10.1126/

science.283.5410.2034.

[2] A.K. Pramanik, A. Banerjee, Griffiths phase and its evolution with Mn-site disorder in the half-doped manganite Pr 0.5 Sr 0.5 Mn 1-y Ga y O 3 (y=0.0, 0.025, and 0.05), Phys. Rev. B - Condens. Matter Mater. Phys. 81 (2010) 024431. Doi:

10.1103/PhysRevB.81.024431.

[3] R.B. Griffiths, Nonanalytic Behavior above the Critical Point in a Random Ising Ferromagnet, Phys. Rev. Lett. 23 (1) (1969) 17–19, https://doi.org/10.1103/

PhysRevLett.23.17.

[4] A.J. Bray, Nature of the Griffiths phase, Phys. Rev. Lett. 59 (5) (1987) 586–589, https://doi.org/10.1103/PhysRevLett.59.586.

[5] S. Banik, I. Das, Evolution from Griffiths like phase to non-Griffiths like phase with Y doping in (La1-xYx)0.7Ca0.3MnO3, J. Magn. Magn. Mater. 469 (2019) 40–45, https://doi.org/10.1016/j.jmmm.2018.08.028.

[6] S.O. Manjunatha, A. Rao, P. Poornesh, W.J. Lin, Y.K. Kuo, Magnetic inhomogeneity and Griffiths phase in Bi substituted La0.65− xBixCa0.35MnO3 manganites, Phys. B Condens. Matter. 498 (2016) 82–91, https://doi.org/10.1016/j.

physb.2016.06.031.

[7] J. Deisenhofer, D. Braak, H.A. Krug Von Nidda, J. Hemberger, R.M. Eremina, V.

A. Ivanshin, A.M. Balbashov, G. Jug, A. Loidl, T. Kimura, Y. Tokura, Observation of a griffiths phase in paramagnetic La1-xSrxMnO3, Phys. Rev. Lett. 95 (2005), https://doi.org/10.1103/PhysRevLett.95.257202.

[8] X.u. Zheng, T. Gao, W. Jing, X. Wang, Y. Liu, B. Chen, H. Dong, Z. Chen, S. Cao, C. Cai, V.V. Marchenkov, Evolution of Griffiths phase and spin reorientation in perovskite manganites, J. Magn. Magn. Mater. 491 (2019) 165611, https://doi.

org/10.1016/j.jmmm.2019.165611.

[9] W. Jiang, XueZhi Zhou, G. Williams, Correlation between phase competition and the nucleation of a Griffiths-like phase in (La 1-y Pr y) 0.7 Ca 0.3 Mn 16/18 O 3, EPL Europhysics Lett. 84 (4) (2008) 47009, https://doi.org/10.1209/0295-5075/

84/47009.

[10] J. Khelifi, A. Tozri, F. Issaoui, E. Dhahri, E.K. Hlil, The influence of disorder on the appearance of Griffiths phase and magnetoresistive properties in (La1-xNdx) 2/3 (Ca1-ySry)1/3MnO3 oxides, Ceram. Int. 40 (1) (2014) 1641–1649, https://doi.

org/10.1016/j.ceramint.2013.07.055.

[11] W. Jiang, X.Z. Zhou, G. Williams, Y. Mukovskii, K. Glazyrin, Griffiths phase and critical behavior in single-crystal La0.7 Ba0.3 Mn O3: Phase diagram for La1-x Bax Mn O3 (x≤0.33), Phys. Rev. B - Condens. Matter Mater. Phys. 77 (2008), 064424, https://doi.org/10.1103/PhysRevB.77.064424.

[12] S. Ghorai, S.A. Ivanov, R. Skini, P. Svedlindh, Evolution of Griffiths phase and critical behaviour of La 1-x Pb x MnO 3±y solid solutions, J. Phys. Condens.

Matter. 33 (14) (2021) 145801–145810, https://doi.org/10.1088/1361-648X/

abdd64.

[13] J. Liu, W.-Q. Wang, H.-Y. Wu, T. Wang, Y. Tian, ⋅ Feng-Ze Cao, ⋅ Ru Xing, Negative Magnetic Entropy Change and Critical Behavior of Manganite La 0.8 Sr 0.2 Mn 1− x Co x O 3 (x 0, 0.2), J. Low Temp. Phys. 195 (2019) 81–95. https://doi.org/

10.1007/s10909-018-02138-7.

[14] J. Lyubina, Magnetocaloric materials for energy efficient cooling, J. Phys. D. Appl.

Phys. 50 (5) (2017) 053002, https://doi.org/10.1088/1361-6463/50/5/053002.

[15] S. Ghorai, R. Skini, D. Hedlund, P. Str¨om, P. Svedlindh, Field induced crossover in critical behaviour and direct measurement of the magnetocaloric properties of La0.4Pr0.3Ca0.1Sr0.2MnO3, Sci. Rep. 10 (2020) 19485, https://doi.org/10.1038/

s41598-020-76321-w.

[16] H.J. Whitlow, G. Possnert, C.S. Petersson, Quantitative mass and energy dispersive elastic recoil spectrometry: Resolution and efficiency considerations, Nucl. Inst.

Methods Phys. Res. B. 27 (3) (1987) 448–457, https://doi.org/10.1016/0168- 583X(87)90527-1.

[17] J.P. Fryns, C. Parloir, J. Deroover, H. Van den Berghe, Tuberous sclerosis.

Bourneville disease., Acta Paediatr. Belg. 31 (1993) suppl V:33-40. https://www.

worldcat.org/title/rietveld-method/oclc/26299196 (accessed July 26, 2019).

[18] Y. Tokura, Y. Tomioka, Colossal magnetoresistive manganites, J. Magn. Magn.

Mater. 200 (1-3) (1999) 1–23, https://doi.org/10.1016/S0304-8853(99)00352-2.

[19] R.D. Shannon, Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides, Acta Crystallogr. Sect. A. 32 (5) (1976) 751–767, https://doi.org/10.1107/S0567739476001551.

[20] A. Tozri, E. Dhahri, E.K. Hlil, Effects of vacancy and Na doping on the structural, magnetic and transport properties of La0.8Pb0.1(□/Na)0.1MnO3, J. Magn. Magn.

Mater. 322 (17) (2010) 2516–2524, https://doi.org/10.1016/j.

jmmm.2010.03.011.

[21] A. Tozri, E. Dhahri, Structural and magnetotransport properties of (La, Pr)-Ba manganites, J. Alloys Compd. 783 (2019) 718–728, https://doi.org/10.1016/j.

jallcom.2018.12.303.

[22] L.B. McCusker, R.B. Von Dreele, D.E. Cox, D. Lou¨er, P. Scardi, Rietveld refinement guidelines, J. Appl. Crystallogr. 32 (1) (1999) 36–50, https://doi.org/10.1107/

S0021889898009856.

[23] M.A. Langell, C.W. Hutchings, G.A. Carson, M.H. Nassir, High resolution electron energy loss spectroscopy of MnO(100) and oxidized MnO(100), J. Vac. Sci.

Technol. A Vacuum, Surfaces, Film. 14 (3) (1996) 1656–1661, https://doi.org/

10.1116/1.580314.

[24] M.S. Kim, J.B. Yang, J. Medvedeva, W.B. Yelon, P.E. Parris, W.J. James, Electronic structure of La 0.7 Sr 0.3 Mn 1–x Cu x O 3 (0.0≤ x ≤0.30), J. Phys. Condens.

Matter. 20 (25) (2008) 255228, https://doi.org/10.1088/0953-8984/20/25/

255228.

[25] A.T. Kozakov, A.G. Kochur, L.A. Reznichenko, L.A. Shilkina, A.V. Pavlenko, A.

V. Nikolskii, K.A. Googlev, V.G. Smotrakov, Single-crystal rare earths manganites La1− x− yBixAyMnαO3±β (A=Ba, Pb): Crystal structure, composition, and Mn ions valence state. X-ray diffraction and XPS study, J. Electron Spectros. Relat.

Phenomena. 186 (2013) 14–24, https://doi.org/10.1016/j.elspec.2013.01.016.

[26] V.R. Galakhov, M. Demeter, S. Bartkowski, M. Neumann, N.A. Ovechkina, E.

Z. Kurmaev, N.I. Lobachevskaya, Y.M. Mukovskii, J. Mitchell, D.L. Ederer, Mn (formula presented) exchange splitting in mixed-valence manganites, Phys. Rev. B - Condens. Matter Mater. Phys. 65 (2002) 1–4, https://doi.org/10.1103/

PhysRevB.65.113102.

[27] H.-S. Lee, H.-H. Park, Band Structure Analysis of La 0.7 Sr 0.3 MnO 3 Perovskite Manganite Using a Synchrotron, Adv. Condens. Matter Phys. 2015 (2015) 1–7, https://doi.org/10.1155/2015/746475.

[28] T. Saitoh, A.E. Bocquet, T. Mizokawa, H. Namatame, A. Fujimori, M. Abbate, Y. Takeda, M. Takano, Electronic structure of La1-xSrxMnO3 studied by photoemission and x-ray-absorption spectroscopy, Phys. Rev. B. 51 (1995) 13942–13951, https://doi.org/10.1103/PhysRevB.51.13942.

[29] K. Ebata, H. Wadati, M. Takizawa, A. Fujimori, A. Chikamatsu, H. Kumigashira, M. Oshima, Y. Tomioka, Y. Tokura, Chemical potential shift and spectral-weight transfer in Pr1-x Cax Mn O3 revealed by photoemission spectroscopy, Phys. Rev. B - Condens. Matter Mater. Phys. 74 (2006), 064419, https://doi.org/10.1103/

PhysRevB.74.064419.

[30] K. Arstila, J. Julin, M.I. Laitinen, J. Aalto, T. Konu, S. K¨arkk¨ainen, S. Rahkonen, M. Raunio, J. Itkonen, J.-P. Santanen, T. Tuovinen, T. Sajavaara, Potku – New

analysis software for heavy ion elastic recoil detection analysis, Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms. 331 (2014) 34–41, https://doi.org/10.1016/j.nimb.2014.02.016.

[31] B.K. Banerjee, On a generalised approach to first and second order magnetic transitions, Phys. Lett. 12 (1) (1964) 16–17, https://doi.org/10.1016/0031-9163 (64)91158-8.

[32] R. Skini, S. Ghorai, P. Str¨om, S. Ivanov, D. Primetzhofer, P. Svedlindh, Large room temperature relative cooling power in La0.5Pr0.2Ca0.1Sr0.2MnO3, J. Alloys Compd. 827 (2020) 154292, https://doi.org/10.1016/j.jallcom.2020.154292.

[33] R. Skini, M. Khlifi, E.K. Hlil, An efficient composite magnetocaloric material with a tunable temperature transition in K-deficient manganites, RSC Adv. 6 (41) (2016) 34271–34279, https://doi.org/10.1039/C5RA27132K.

[34] R. Skini, A. Omri, M. Khlifi, E. Dhahri, E.K. Hlil, Large magnetocaloric effect in lanthanum-deficiency manganites La 0.8-x□xCa0.2MnO3 (0.00≤x≤0.20) with a first-order magnetic phase transition, J. Magn. Magn. Mater. 364 (2014) 5–10, https://doi.org/10.1016/j.jmmm.2014.04.009.

[35] P. Radaelli, G. Iannone, M. Marezio, Structural effects on the magnetic and transport properties of perovskite 0.30), Phys. Rev. B - Condens. Matter Mater.

Phys. 56 (1997) 8265–8276, https://doi.org/10.1103/PhysRevB.56.8265.

[36] J. Yang, W.H. Song, Y.Q. Ma, R.L. Zhang, B.C. Zhao, Z.G. Sheng, G.H. Zheng, J.

M. Dai, Y.P. Sun, Structural, magnetic, and transport properties of the Cu-doped manganite La0.85Te0.15Mn1-xCuxO3 (0 ≤ x ≤ 0.20), Phys. Rev. B - Condens.

Matter Mater. Phys. 70 (2004), 092504, https://doi.org/10.1103/

PhysRevB.70.092504.

[37] F. Bridges, L. Downward, J.J. Neumeier, T.A. Tyson, Detailed relationship between local structure, polarons, and magnetization for La 1?xCa xMnO 3 (0.21≥x≥0.45), Phys. Rev. B - Condens. Matter Mater. Phys. 81 (2010), 184401, https://doi.org/

10.1103/PhysRevB.81.184401.

[38] P.S.A. Kumar, P.A. Joy, S.K. Date, Evidence for Jahn-Teller polaron formation and spin-cluster-assisted variable-range-hopping conduction in La0.7Ca0.3MnO3, J. Phys. Condens. Matter. 10 (17) (1998) L269–L275, https://doi.org/10.1088/

0953-8984/10/17/001.

[39] L. Downward, F. Bridges, S. Bushart, J.J. Neumeier, N. Dilley, L. Zhou, Universal relationship between magnetization and changes in the local structure of La1- xCaxMnO3: Evidence for magnetic dimers, Phys. Rev. Lett. 95 (2005), 106401, https://doi.org/10.1103/PhysRevLett.95.106401.

[40] H. Zhang, L. Chen, Y. Li, H. Liu, Y. Chen, K. Chen, X. Dong, H. Yang, T. Gao, Q. Li, Griffiths phase and disorder in perovskite manganite oxides La 1-x Ca x MnO3 and La 0.7Sr 0.3MnO3, in: J. Supercond. Nov. Magn., 2011: pp. 1665–1672. Doi:

10.1007/s10948-010-1081-5.

[41] A. Chanda, U. Chaudhuri, R. Das, R. Mahendiran, Broadband magnetotransport in La0.6Sr0.4Mn1-xGaxO3 (0.01 > x > 0.3) at room temperature, J. Appl. Phys. 126 (2019), https://doi.org/10.1063/1.5109738.