Study on mechanism of novel magnetic phase transitions and anomalous transport properties in rare earth sulfides

为了阐明稀土硫化物a-R_2S_3（R：稀土元素）中新的磁相变机制和与相变有关的反常输运性质，进行了磁化强度、磁场电阻率、比热和霍尔效应的测量。a-R_2S_3有两个不等价的R位。发现除R=Gd外的a-R_2S_3都表现出连续的磁相变，在此相变时，每个R格上的磁矩都是有序的。同时也阐明了稀土原子基态在各格位上的多重性。此外，还发现了一些新的物理性质，如α- Sm_2S_3在很窄的温度范围内电阻率有很大的突变。

In order to elucidate the mechanism of novel magnetic phase transitions and anomalous transport properties associated with the transitions in rare earth sulfides a-R_2S_3 (R : rare earth elements), measurements of magnetization and electrical resistivity in magnetic fields, specific heat and the Hall effect have been carried out. The a-R_2S_3 has two inequivalent R sites. It has been found out that the a-R_2S_3 except R=Gd shows successive magnetic phase transitions at which the magnetic moments on each R site order. The multiplicity of the ground state of rare earth atom on each site has also been clarified. Furthermore, novel physical properties were discovered ; one example is that the a- Sm_2S_3 shows an extremely large abrupt increase and decrease of electrical resistivity in a narrow temperature range.