Dalal Biswajit, Sarkar Babusona, Dev Ashok Vishal, De S K
Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700032, India.
J Phys Condens Matter. 2016 Oct 26;28(42):426001. doi: 10.1088/0953-8984/28/42/426001. Epub 2016 Aug 24.
Magnetic properties of YbCr1-x Ru x O3 as a function of temperature and magnetic field have been investigated to explore the intriguing magnetic phenomena in rare-earth orthochromites. A quantitative analysis of x-ray photoelectron spectroscopy confirms the mixed valence state (Yb(3+) and Yb(2+)) of Yb ions for the highest doped sample. Field-cooled magnetization reveals a broad peak around 75 K and then becomes zero at about 20-24 K, due to the antiparallel coupling between Cr(3+) and Yb(3+) moments. An increase of the Ru(4+) ion concentration leads to a slight increase of compensation temperature T comp from 20 to 24 K, but the Néel temperature remains constant. A larger value of the magnetic moment of Yb ions gives rise to negative magnetization at low temperature. An external magnetic field significantly modifies the temperature dependent magnetization. Simulation of temperature dependent magnetization data, below T N, based on the three (two) magnetic sub-lattice model predicts stronger intra-sublattice exchange interaction than that of inter-sublattice. Thermal hysteresis and Arrot plots suggest first order magnetic phase transition. Random substitution of Ru(4+) ion reduces the magnetic relaxation time. Weak ferromagnetic component in canted antiferromagnetic system and negative internal magnetic field cause zero-field-cooled exchange bias effect. Large magnetocrystalline anisotropy associated with Ru creates high coercivity in the Ru doped sample. A maximum value of magnetocaloric effect is found around the antiferromagnetic ordering of Yb(3+) ions. Antiferromagnetic transition at about 120 K and temperature induced magnetization reversal lead to normal and inverse magnetocaloric effects in the same material.
对YbCr1-xRuxO3的磁性随温度和磁场的变化进行了研究，以探索稀土正铬酸盐中有趣的磁现象。对最高掺杂样品的X射线光电子能谱定量分析证实了Yb离子的混合价态（Yb(3+)和Yb(2+)）。场冷磁化强度在75K左右出现一个宽峰，然后在约20 - 24K时变为零，这是由于Cr(3+)和Yb(3+)磁矩之间的反平行耦合。Ru(4+)离子浓度的增加导致补偿温度Tcomp从20K略微增加到24K，但奈尔温度保持不变。Yb离子较大的磁矩值在低温下会产生负磁化强度。外部磁场显著改变了随温度变化的磁化强度。基于三（两）磁子晶格模型对低于TN的随温度变化的磁化强度数据进行模拟，预测子晶格内的交换相互作用比子晶格间的更强。热滞回线和阿罗特图表明存在一级磁相变。Ru(4+)离子的随机取代降低了磁弛豫时间。倾斜反铁磁系统中的弱铁磁成分和负内磁场导致零场冷交换偏置效应。与Ru相关的大磁晶各向异性在Ru掺杂样品中产生了高矫顽力。在Yb(3+)离子的反铁磁有序附近发现了磁热效应的最大值。约120K的反铁磁转变和温度诱导的磁化反转在同一材料中导致了正常和逆磁热效应。
