Centre of Low Temperature Physics, P J Šafárik University and IEP SAS, Park Angelinum 9, SK-04154 Košice, Slovakia.
J Phys Condens Matter. 2013 May 8;25(18):186003. doi: 10.1088/0953-8984/25/18/186003. Epub 2013 Apr 16.
We report on a comprehensive investigation of the magnetic properties of [NdCo(bpdo)(H2O)4(CN)6]⋅3H2O (bpdo=4, 4'-bipyridine-N,N'-dioxide) by use of electron paramagnetic resonance, magnetization, specific heat and susceptibility measurements. The studied material was identified as a magnet with an effective spin S = 1/2 and a weak exchange interaction J/kB = 25 mK. The ac susceptibility studies conducted at audio frequencies and at temperatures from 1.8 to 9 K revealed that the application of a static magnetic field induces a slow spin relaxation. It is suggested that the relaxation in the magnetic field appears due to an Orbach-like process between the two lowest doublet energy states of the magnetic Nd(3+) ion. The appearance of the slow relaxation in a magnetic field cannot be associated with a resonant phonon trapping. The obtained results suggest that the relaxation is influenced by nuclear spin driven quantum tunnelling which is suppressed by external magnetic field.
我们通过电子顺磁共振、磁化、比热和磁化率测量，对[NdCo(bpdo)(H2O)4(CN)6]⋅3H2O（bpdo=4,4'-联吡啶-N,N'-二氧化物）的磁性进行了全面研究。所研究的材料被确定为具有有效自旋 S=1/2 和弱交换相互作用 J/kB=25mK 的磁体。在音频频率和 1.8 至 9 K 的温度下进行的交流磁化率研究表明，施加静态磁场会导致自旋弛豫缓慢。据推测，磁场中的弛豫是由于磁 Nd(3+)离子的两个最低双重态之间的 Orbach 型过程引起的。磁场中出现缓慢弛豫不能与共振声子俘获相关联。所得结果表明，弛豫受核自旋驱动量子隧穿的影响，而外部磁场抑制了量子隧穿。
