Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
J Phys Condens Matter. 2011 Apr 27;23(16):164218. doi: 10.1088/0953-8984/23/16/164218. Epub 2011 Apr 6.
We report magnetization data for several titanium pyrochlore systems measured down to 0.5 K. The measurements, performed on single crystal samples in fields of up to 7 kOe, have captured the essential elements of the previously reported phase transitions in these compounds and have also revealed additional important features overlooked previously either because of the insufficiently low temperatures used, or due to limitations imposed by polycrystalline samples. For the spin-ice pyrochlores Dy(2)Ti(2)O(7) and Ho(2)Ti(2)O(7), an unusually slow relaxation of the magnetization has been observed in lower fields, while the magnetization process in higher fields is essentially hysteresis-free and does not depend on sample history. For the XY pyrochlore Er(2)Ti(2)O(7), the magnetic susceptibility shows nearly diverging behaviour on approach to a critical field, H(C) = 13.5 kOe, above which the magnetization does not saturate but continues to grow at a significant rate. For the Heisenberg pyrochlore Gd(2)Ti(2)O(7), the magnetic susceptibility shows a pronounced change of slope at both transition temperatures, T(N1) = 1.02 K and T(N2) = 0.74 K, contrary to the earlier reports.
我们报告了几种钛烧绿石系统的磁化数据，这些数据是在低至 0.5 K 的温度下测量的。这些测量是在高达 7 kOe 的磁场下对单晶样品进行的，它们捕捉到了这些化合物中以前报道的相变的基本要素，同时也揭示了以前由于温度不够低或由于多晶样品的限制而忽略的其他重要特征。对于自旋冰烧绿石 Dy(2)Ti(2)O(7)和 Ho(2)Ti(2)O(7)，在较低的磁场下观察到磁化的异常缓慢弛豫，而在较高的磁场下，磁化过程基本上是无滞后的，并且不依赖于样品历史。对于 XY 烧绿石 Er(2)Ti(2)O(7)，磁导率在接近临界场 H(C) = 13.5 kOe 时表现出几乎发散的行为，在该场以上，磁化不会饱和，而是以显著的速率继续增长。对于海森堡烧绿石 Gd(2)Ti(2)O(7)，磁导率在两个相变温度 T(N1) = 1.02 K 和 T(N2) = 0.74 K 处都表现出明显的斜率变化，这与早期的报告相反。
