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|Title:||Critical behavior of La0.7Ca0.3Mn1-xNixO3 manganites exhibiting the crossover of first- and second-order phase transitions|
Tran, Q. T.
Thanh, P. Q.
|Keywords:||Perovskite manganites;Critical behavior;Magnetic entropy change|
|Publisher:||PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND|
|Abstract:||We used Banerjee0 s criteria, modified Arrott plots, and the scaling hypothesis to analyze magnetic-field dependences of magnetization near the ferromagnetic–paramagnetic (FM–PM) phase-transition tem-perature (TC) of perovskite-type manganites La0.7Ca0.3Mn1 x NixO3 (x¼0.09, 0.12 and 0.15). In the FM region, experimental results for the critical exponent β(¼0.171 and 0.262 for x¼0.09 and 0.12, respectively) reveal twofirst samples exhibiting tricriticality associated with the crossover offirst- and second-order phase transitions. Increasing Ni-doping content leads to the shift of theβvalue (¼0.320 for x¼0.15) towards that expected for the 3D Ising model (β¼0.325). This is due to the fact that the substitution of Ni ions into the Mn site changes structural parameters and dilutes the FM phase, which act asfluctuations and influence the FM-interaction strength of double-exchange Mn 3þ –Mn4þ pairs, and the phase-transition type. For the critical exponent γ (¼0.976–0.990), the stability in its value demonstrates the PM behavior aboveTCof the samples. Particularly, aroundTCof La0.7Ca0.3Mn1 x NixO3 compounds, magnetic-field dependences of the maximum magnetic-entropy change can be described by a power law of |ΔSmax|pH n , where values n¼0.55–0.77 are quite far from those (n¼0.33–0.48) calculated from the theoretical relationn¼1þ(β 1)/(βþγ). This difference is related to the use of the mean-field theory for the samples exhibiting the magnetic inhomogeneity.|
|Description:||SOLID STATE COMMUNICATIONS Volume: 184 Pages: 40-46 Published: APR 2014|
|Appears in Collections:||Bài báo của ĐHQGHN trong Web of Science|
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