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

自高温超导体被发现以来，从强相关电子系统的角度出发，人们对低维过渡金属氧化物给予了极大的关注。一些具有辉绿岩型结构的氧化物因其低维三角形结构而受到人们的关注。CuFeO_2具有磁性的Fe^<3+>层，形成层状三角形晶格的反铁磁体，由非磁性的Cu^+和O^<2->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。CuFeO_2在13k （T_<N1>）和9k （T_<N2>）下表现出两次连续的反铁磁跃迁。另一种反铁磁氧化物CuCrO_2和透明半导体CuAlO_2也进行了研究。由于杂质在很大程度上影响了CuFeO_2的反铁磁性，因此压力效应有望影响其磁性状态。本研究对CuFeO_2在高压下的反铁磁传导温度进行了磁化率测量，并对CuCrO_2和CuAlO_2在高压下的电阻率进行了测量。从CuFeO_2的磁化率测量结果来看，当压力达到0.7 GPa时，T_<N1>和T_<N2>以-1K/GPa的速率降低。如果T_<N1>和T_<N2>以-1 K/GPa的速率线性下降，则在10 GPa时消失。然后，在超过10gpa的高压下进行高压研究是非常有趣的，因为在磁性有序态消失的压力下，可以预期出现新的磁相，就像在UGe_2中观察到的那样。从高压下的电阻率初步测量结果来看，在10gpa时，电阻率降至0.1倍。在更高的压力下进行磁化率和电阻率测量。在高压下CuCrO_2和CuAlO_2的电阻率测量中，电阻率随压力的增加略有下降。更高压力下的电阻率测量正在进行中。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