High-pressure studies of antiferromagnetic oxides with a delafossite-type triangular structure

自从高T_c超导体被发现以来，从强关联电子系统的角度来看，低维过渡金属氧化物受到了极大的关注。一些具有氟磷矿型结构的氧化物由于其低维的三角形结构而引起了人们的关注。CuFeO_2具有磁性的Fe^&lt；3+&gt；层，形成层状的三角形晶格受挫反铁磁体，由非磁性的Cu^+和O^&lt；2-&gt；层隔开。在受挫系统中，磁相变发生在磁相互作用的微妙平衡下。CuFeO2在13K(T&lt；n1&gt；)和9K(T&lt；n2&gt；)表现出两个连续的反铁磁相变。还研究了另一种反铁磁性氧化物CuCrO_2和透明半导体CuAlO_2。由于杂质对CuFeO_2的反铁磁性有很大影响，压力效应可能会影响其磁态。在本研究中，我们对反铁磁性的tra-…进行了磁化率测量。CuFeO_2在高压下的更高温度以及在高压下对CuCrO_2和CuAlO_2的电阻率测量。从CuFeO_2的磁化率测量结果来看，T_t；n1&gt；和T_&lt；n2&gt；在-1K/GPA的压力下，随着压力的升高而减小。如果T_&lt；n1&gt；和T_&lt；n2&gt；以-1K/GPA的速率线性下降，则它在10 GPA时消失。因此，在10 Gpa以上进行高压研究是非常有趣的，因为在UGe_2中观察到的磁有序态消失的压力下可能会出现一个新的磁相。从高压下的初步电阻率测量来看，在10 Gpa时，电阻率下降到0.1倍。磁化率和电阻率的测量在较高的压力下进行。在高压下测量CuCrO_2和CuAlO_2的电阻率时，随着压力的增加，其电阻率略有下降。在更高压力下的电阻率测量正在进行中。较少

Since the high-Tc superconductor was discovered, great attension has been paid to low-dimensional transition metal oxides, from the view of strongly correlated electron systems. Some oxides with a delafossite-type structure have been attractive because of its low-dimensional triangular structure. CuFeO_2 has magnetic Fe^<3+> layers, which form a layered triangular lattice frustrated antiferromagnet, separated by nonmagnetic Cu^+ and O^<2-> layers. In a frustrated system, the magnetic phase transitions take place under a subtle balance of magnetic interactions. CuFeO_2 exhibits two successive antiferromagnetic transitions at 13 K(T_<N1>) and 9 K (T_<N2>). Another antiferromagnetic oxides, CuCrO_2 and transparent semiconductor, CuAlO_2 have also been investigated. Since impurity largely affects the antiferromagnetism of CuFeO_2, the pressure effect is expected to affect the magnetic state. In this study we have carried out magnetic susceptibility measurements on the antiferromagnetic tra … More nsition temperature of CuFeO_2 under high pressure and electrical resistivity measurements on CuCrO_2 and CuAlO_2 under high pressure. From the magnetic susceptibility measurements of CuFeO_2, the T_<N1> and T_<N2> decrease with pressure up to 0.7 GPa at a rate of -1K/GPa. If the T_<N1> and T_<N2> decrease linearly at a rate of -1 K/GPa, it disappears at 10 GPa. Then it is very interesting to perform high-pressure studies at more than 10 GPa, since a new magnetic phase can be expected at the pressure where the magnetic ordering state disappears, as observed in UGe_2. From the preliminary electrical resistivity measurements under high pressure, the resistivity decreases to 0.1 times value at 10 GPa. The susceptibility and electrical resisitivity measurements are in progress at_higher pressures. In the electrical resistivity measurements of CuCrO_2 and CuAlO_2 under high pressure, the resistivity decreases a little with increasing pressure. The resistivity measurements under much higher pressure are in progress. Less