Institute of Mathematics, Physics and Mechanics, Jadranska 19, 1000 Ljubljana, Slovenia.
J Phys Condens Matter. 2012 Feb 8;24(5):056002. doi: 10.1088/0953-8984/24/5/056002. Epub 2012 Jan 17.
The magnetic properties of layered hydroxylammonium fluorocobaltate (NH(3)OH)(2)CoF(4) were investigated by measuring its dc magnetic susceptibility in zero-field-cooled (ZFC) and field-cooled (FC) regimes, its frequency dependent ac susceptibility, its isothermal magnetization curves after ZFC and FC regimes, and its heat capacity. Effects of pressure and magnetic field on magnetic phase transitions were studied by susceptibility and heat capacity measurements, respectively. The system undergoes a magnetic phase transition from a paramagnetic state to a canted antiferromagnetic state exhibiting a weak ferromagnetic behavior at T(C) = 46.5 K and an antiferromagnetic transition at T(N) = 2.9 K. The most spectacular manifestation of the complex magnetic behavior in this system is a shift of the isothermal magnetization hysteresis loop in a temperature range below 20 K after the FC regime-an exchange bias phenomenon. We investigated the exchange bias as a function of the magnetic field during cooling and as a function of temperature. The observed exchange bias was attributed to the large exchange anisotropy which exists due to the quasi-2D structure of the layered (NH(3)OH)(2)CoF(4) material.
层状羟基氨合氟合钴酸盐 (NH(3)OH)(2)CoF(4) 的磁性通过测量其在零场冷却 (ZFC) 和场冷却 (FC) 状态下的直流磁化率、频率相关的交流磁化率、ZFC 和 FC 状态后的等温磁化曲线以及其热容来研究。通过磁化率和热容测量分别研究了压力和磁场对磁相变的影响。该系统经历了从顺磁态到倾斜反铁磁态的磁相变，在 T(C) = 46.5 K 处表现出弱铁磁行为，在 T(N) = 2.9 K 处发生反铁磁转变。在这个系统中，复杂磁行为最显著的表现是在 FC 状态后，在低于 20 K 的温度范围内等温磁化磁滞回线的偏移，即交换偏置现象。我们研究了冷却过程中磁场和温度对交换偏置的影响。观察到的交换偏置归因于由于层状 (NH(3)OH)(2)CoF(4) 材料的准二维结构而存在的大交换各向异性。
