多铁性铬氧化物YCrO_3体系的磁特性及比热研究

Magnetic Properties and Specific Heat on Multiferroics YCrO_3 Chromites

系统研究了低温条件下铬氧化物YCrO3体系的磁特性及比热特点。实验结果表明,在高温区(T>140 K)直流磁化率随温度的变化遵从居里-外斯定律,YCrO3体系处于顺磁状态,样品的有效平均磁矩μeff=3.99μB、顺磁居里-外斯温度TCW=-340 K,即体系具有反铁磁性。在TN=140 K附近,YCrO3体系经历了由顺磁态向倾角反铁磁态的相转变,其自旋磁结构一直保持为Г4(Gx,Ay,Fz;FzR);低温条件下(T<140 K),体系具有完整闭合的磁滞回线,表明YCrO3样品具有反铁磁性的同时,具有明显的弱铁磁性,且随温度的降低铁磁性逐渐增强。对应于磁相变温度TN,比热曲线在140 K附近出现尖锐的λ形反常突起,由于Y离子没有磁性,显示了Cr3+磁矩亚晶格的顺磁-反铁磁相变对比热的贡献。

The magnetic and specific-heat properties were systemically investigated for multiferroic YCrO3 chromites with a temperature range of 2.0 - 300 K. The results showed that the susceptibility followed the Curie-Weiss law at elevated temperature. The corre- sponding effective magnetic moment μeff = 3.99μB and asymptotic paramagnetic Curie temperature Tcw= -340 K, suggested the predominance of antiferromag- netic interactions in YCrO3 chromites, At TN = 140 K, YCrO3 possessed a significant transition of the Cr sublattice from a paramagnetic to a canted antiferromagnetic （CAFM） order. The allowed spin configurations were denoted as Г4 （ GxAyFz ; Fz ）. Simultaneously, the hysteretic loops confirmed the canted antiferromag- netic behaviors, where the ferromagnetic contribution increased with lowering the temperature. Furthermore, the specific heat data showed the typical second order phase transition from paramagnetic to CAFM ordering at TN = 140 K. Owing to the nonmagnetic property of y3＋, the present results exhibited the interaction of the canted Cr3＋ moments, and it would be helpful to understanding the physical mechanism and have possi- ble application for multiferroic YCrO3 chromites.