# Study of the magnetic behavior of single-crystalline Nd0.5Sr0.5MnO3

TL;DR: In this paper, zero-field cooling and field-cooled magnetization data in single-crystalline Nd0.5Sr 0.5MnO3 revealed the existence of thermodynamic irreversibility below Curie temperature (TC), indicating the presence of frustration of spins.

Abstract: Zero-field-cooled and field-cooled magnetization data in single-crystalline Nd0.5Sr0.5MnO3 revealed the existence of thermodynamic irreversibility below Curie temperature (TC), indicating the presence of frustration of spins. The imaginary part of ac susceptibility (χ″) indicates a prominent cusp below TC, which shifts to higher temperatures with increasing frequency. Magnetization, ac susceptibility, resistivity, and specific-heat measurements were used to find three critical exponents α=0.12(1), β=0.5(0), and γ=1.02(2). The values of the critical exponents are all between mean-field values and three-dimensional Heisenberg model values.

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TL;DR: In this article, the authors have prepared polycrystalline samples La 0.7 Ca 0.3- x Ba x MnO 3 materials in magnetic refrigeration and studied their magnetic properties and magnetocaloric effect based on magnetization versus temperature and magnetic-field measurements.

Abstract: We have prepared polycrystalline samples La 0.7 Ca 0.3- x Ba x MnO 3 ( x = 0, 0.025, 0.05, 0.075 and 0.1) by solid-state reaction, and then studied their magnetic properties and magnetocaloric (MC) effect based on magnetization versus temperature and magnetic-field ( M – H – T ) measurements. Experimental results reveal the easiness in tuning the Curie temperature ( T C ) from 260 to about 300 K by increasing Ba-doping concentration ( x ) from 0 to 0.1. Under an applied field H = 50 kOe, maximum magnetic-entropy changes around T C of the samples can be tuned in the range between 6 and 11 J kg −1 K −1 , corresponding to refrigerant-capacity values ranging from 190 to 250 J kg −1 . These values are comparable to those of some conventional MC materials, and reveal the applicability of La 0.7 Ca 0.3- x Ba x MnO 3 materials in magnetic refrigeration. Analyses of the critical behavior based on the Banerjee criteria, Arrott plots and scaling hypothesis for M – H – T data prove a magnetic-phase separation when Ba-doping concentration changes. In the doping region x = 0.05–0.075, the samples exhibits the crossover of first- and second-order phase transitions with the values of critical exponents β and γ close to those expected for the tricritical mean-field theory. The samples with x x > 0.075 exhibit first- and second-order transitions, respectively. More detailed analyses related to the Griffiths singularity, the critical behavior for different magnetic-field intervals started from 10 kOe, and the magnetic-ordering parameter n = dLn|Δ S m |/dLn H (where Δ S m is the magnetic-entropy change) demonstrate magnetic inhomogeneities and multicritical phenomena existing in the samples.

70 citations

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TL;DR: In this paper, the magnetocaloric effect in perovskite manganite Nd0.55Sr0.45MnO3 was investigated and the maximum magnetic entropy change and the highest relative cooling power under magnetic field variation of 3.0 T were found to be 3.12 and 70.87 T, respectively.

Abstract: In this paper, we have investigated the magnetocaloric effect in perovskite manganite Nd0.55Sr0.45MnO3. The maximum magnetic entropy change and the highest relative cooling power under magnetic field variation of 3.0 T are found to be 3.12 J/kg K and 70.87 J/kg, respectively. Based on the obtained magnetic entropy change under different magnetic fields, we have calculated the spontaneous magnetization which persistently increases with the decrease of temperatures. For comparison, the spontaneous magnetization has been also deduced from the Arrott plot. The excellent agreement between the two methods confirms that the utilization of magnetic entropy change to get the spontaneous magnetization is valid. Besides, we also calculated the critical exponent β which value is about 0.452, indicating that the observed ferromagnetic phase transition in the present material can be approximatively understood with mean field model.

30 citations

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TL;DR: In this paper, structural, magnetic and magnetocaloric properties of GdFeO3-type Pr0.5Eu0.1Sr0.4MnO3 manganites were investigated in details for the Gd FeO3 type Pr0,5EU0.

Abstract: The structural, magnetic and magnetocaloric properties are investigated in details for the GdFeO3-type Pr0.5Eu0.1Sr0.4MnO3 and Pr0.5Er0.1Sr0.4MnO3 manganites (oP20, space group Pnma, N 62). Landau analysis, Banerjee’s criteria, and universal behaviour are studied to assess magnetic ordering in the samples. These methods reveal the occurrence of a second-order phase transition and the short-range interactions in the vicinity of Curie temperatures. The maximum of the magnetic entropy change ΔSM (field change of 5 T) is found to increase from 4.47 J/kg.K at TC = 279.9 ± 1 K to 4.86 J/kg.K at TC = 188.5 ± 1 K for Pr0.5Eu0.1Sr0.4MnO3 and Pr0.5Er0.1Sr0.4MnO3, respectively with corresponding relative cooling power (RCP) 264.8 J/kg to 270.9 J/kg.

30 citations

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TL;DR: In this paper, the authors used modified Arrott plots and scaling hypothesis to analyze magnetic-field dependences of magnetization near the ferromagnetic-paramagnetic (FM-PM) phase-transition temperature.

Abstract: We used Banerjee’s criteria, modified Arrott plots and scaling hypothesis to analyze magnetic-field dependences of magnetization near the ferromagnetic–paramagnetic (FM–PM) phase-transition temperature ( T C ) of Nd 0.67 Ba 0.33 Mn 1− x Fe x O 3 ( x =0 and 0.02) manganites. Experimental results reveal that the two samples undergo a second-order phase transition and a critical exponents values ( β =0.326±0.005, γ =1.244±0.033, δ =4.740 at T C =145 K for x =0 and β =0.509±0.013, γ =1.140±0.117 and δ =3.011 at T C =134 K for x =0.02) slightly shifting from those of the 3D-Ising model and the mean field model, respectively. These exponents indicate that the exchange interaction J ( r ) ranges from r − 5 and r − 4.5 for x =0 (respectively J ( r ) r − 5 , for x =0.02). This is due to the fact that the substitution of Fe ions into the Mn site leads to the formation of a larger proportion of Mn 4+ with respect to Mn 3+ which reduces the ferromagnetic double-exchange interaction of Mn 3+ –Mn 4+ couples. By investigating the field dependence of the magnetic entropy change Δ S M , it was possible to evaluate the critical exponents of the magnetic phase transitions. Their values are in good agreement with those obtained from the critical exponents using a modified Arrott method.

18 citations

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TL;DR: In this paper, the effect of both synthesis routes on the physical properties of charge-ordered manganites was investigated, and the results confirmed the second-order character of the manganite.

Abstract: We investigated the effect of both synthesis routes on the physical properties of charge-ordered Pr0.5Sr0.5MnO3 (PSMO) manganites. The samples are prepared by the solid-state reaction (SSR) and the modified sol-gel (SG) method. X-ray diffraction (XRD), SEM and magnetic measurement are used to study the structural, morphological, magnetic, magnetocaloric effect and the critical behaviour of our manganites. XRD studies confirmed the single phase orthorhombic formation of PSMO. Both compounds undergo two successive magnetic phase transitions with the variation of temperature: a paramagnetic (PM)-to-ferromagnetic (FM) transition around $ T_{\rm C}=265$
and 243K followed by an FM-to-antiferromagnetic charge-ordered transition at $ T_{\rm CO}=85$
and 159K for the SG and SSR methods, respectively. Moreover, Banerjee's criteria, Landau analysis and universal curves of phase transitions are also studied to access the magnetic ordering of the PM-FM transition in the samples and confirmed the second-order character. Critical exponents associated with the ferromagnetic phase transition are analyzed and found to be inconsistent with any known universality class. Important magnetic entropy changes and the relative cooling power (RCP) were observed in the sample synthesized through the solid state method as compared to the sol-gel-synthesized sample. The PSMO compounds show both negative ( $ \Delta S_{\rm M}=-1.63813$
J/kgK for SSR and -1.1 for SG) as well as positive ( $ \Delta S_{\rm M}=+5.82$
J/kgK for SSR and +1.52 for SG) magnetocaloric effects under a 2T field at ferromagnetic and charge order transitions, respectively. This feature of successive inverse and normal MCEs in Pr0.5Sr0.5MnO3 are suggested to be applied in some magnetic refrigerators with special designs and functions.

12 citations

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TL;DR: In this article, it was shown that the dominant contribution to the magnetic resistivity of a metal is due to the short-range spin fluctuations and hence that the magnetic specific heat should vary like the magnet specific heat.

Abstract: By general arguments it is shown that the dominant contribution to the magnetic resistivity ${\ensuremath{\rho}}_{\mathrm{mag}}$ of a metal is due to the short-range spin fluctuations and hence that $\frac{d{\ensuremath{\rho}}_{\mathrm{mag}}}{\mathrm{dT}}$ should, in the static approximation, vary like the magnetic specific heat.

647 citations

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TL;DR: In this paper, the ferromagnetic-to-paramagnetic phase transition was found at 346 K and four critical exponents were measured as: ''ensuremath{\alpha}=0.05\ifmmode\pm\p\else\textpm\fi{}0.27'' ifmmode/p\p+1.

Abstract: Magnetization, susceptibility, and specific heat measurements were made on a single crystal of ${\mathrm{La}}_{0.75}{\mathrm{Sr}}_{0.25}{\mathrm{MnO}}_{3}.$ The ferromagnetic-to-paramagnetic phase transition was found at 346 K and four critical exponents were measured as: $\ensuremath{\alpha}=0.05\ifmmode\pm\else\textpm\fi{}0.07,$ $\ensuremath{\beta}=0.40\ifmmode\pm\else\textpm\fi{}0.02,$ $\ensuremath{\gamma}=1.27\ifmmode\pm\else\textpm\fi{}0.06,$ and $\ensuremath{\delta}=4.12\ifmmode\pm\else\textpm\fi{}0.33.$ The values of critical exponents are all between mean-field values and three-dimensional-(3D)-Ising-model values. The scaling behavior is well obeyed for all measurements, and the associated exponent relations are well satisfied, validating the critical analysis. Although the cubic crystal structure of this material makes the 3D Heisenberg the expected model, uniaxial magnetic anisotropy arising from the shape of the sample causes the 3D Ising model to be important within the experimental temperature range.

136 citations

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TL;DR: In this paper, the critical exponents associated with the ferromagnetic transition have been determined from ac susceptibility and dc magnetization data using techniques like the Kouvel-Fischer plots, the modified Arrots plots, and the critical isotherm analysis.

Abstract: We report measurements and analysis of the magnetic critical phenomena in a single crystal of ${\mathrm{La}}_{0.875}{\mathrm{Sr}}_{0.125}{\mathrm{MnO}}_{3}.$ The critical exponents associated with the ferromagnetic transition have been determined from ac susceptibility and dc magnetization data. Techniques like the Kouvel-Fischer plots, the modified Arrots plots, and the critical isotherm analysis were used for this purpose. The values of the exponents $\ensuremath{\gamma},$ $\ensuremath{\beta},$ and $\ensuremath{\delta}$ obtained are found to match very well with those predicted for the three-dimensional Heisenberg model. Our results are consistent with recent numerical calculations and suggest that though the double exchange interaction is driven by the motion of conduction electrons, the effective magnetic interaction near the transition is renormalized to a short range one.

53 citations

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TL;DR: It is found that the electron or hole character of the charge carrier depends on the static JT distortion and due to the two-component nature of the JT coupling, fluctuations in theJT distortion direction contribute to the charge transport in similar fashion as the local spins.

Abstract: Jahn-Teller (JT) electron-phonon-coupling effects in the colossal-magnetoresistance perovskite compounds ${\mathrm{La}}_{1\ensuremath{-}x}{A}_{x}\mathrm{Mn}{\mathrm{O}}_{3}$ are investigated. Electron-electron correlations between two degenerate Mn ${e}_{g}$ orbitals are studied in the Gutzwiller approximation. The static JT distortion and nonadiabatic polaron effects are studied in a modified Lang-Firsov approximation. We find that (i) the electron or hole character of the charge carrier depends on the static JT distortion and (ii) due to the two-component nature of the JT coupling, fluctuations in the JT distortion direction contribute to the charge transport in similar fashion as the local spins.

53 citations

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TL;DR: In this article, the Jahn-Teller (JT) electron-phonon coupling effects in the colossal magnetoresistance perovskite compounds $La_{1-x}A_xMnO_3$ are investigated.

Abstract: Jahn-Teller (JT) electron-phonon coupling effects in the colossal magnetoresistance perovskite compounds $La_{1-x}A_xMnO_3$ are investigated. Electron-electron correlations between two degenerate Mn $e_g$ orbitals are studied in the Gutzwiller approximation. The static JT distortion and antiadiabatic polaron effects are studied in a modified Lang-Firsov approximation. We find that (i) the electron or hole character of the charge carrier depends on the static JT distortion, and (ii) due to the two-component nature of the JT coupling, fluctuations in the JT distortion direction contribute to the charge transport in similar fashion as the local spins.

44 citations