Institute for Condensed Matter Physics, TU Braunschweig, Braunschweig, Germany.
J Phys Condens Matter. 2011 Jun 1;23(21):216001. doi: 10.1088/0953-8984/23/21/216001. Epub 2011 May 9.
The magnetic phase diagram of multiferroic MnWO(4) is studied in magnetic fields up to 60 T using sound velocity and sound attenuation measurements. Anomalies are observed at temperatures T(N1) = 7.6 K, T(N2) = 12.6 K and T(N3) = 13.6 K that separate commensurate antiferromagnetic (AF1) to helical AF2 and commensurate AF3 to paramagnetic phases, respectively. The anomalies are significantly different and shed light on the spin-phonon coupling and evolution of the various order parameters in this multiferroic material. For temperatures below T(N2) pronounced field hysteresis effects are also observed in the sound velocity, indicating field-induced transformations. In the temperature dependence of the attenuation we observe anomalies distinctively different from the usual maxima related to relaxation effects. They are attributed to the combination of dispersion effects due to domain walls and the discontinuously changing sound velocity. In total, six different magnetic phases, at various temperatures and fields including a novel high-field phase, are revealed and analyzed.
多铁性 MnWO(4) 的磁相图在高达 60 T 的磁场中使用声速和衰减测量进行了研究。在温度 T(N1)=7.6 K、T(N2)=12.6 K 和 T(N3)=13.6 K 处观察到了异常，这些异常分别将准同型反铁磁 (AF1) 分离为螺旋 AF2 和准同型 AF3 到顺磁相。这些异常明显不同，揭示了自旋-声子耦合和这种多铁材料中各种有序参数的演变。在低于 T(N2)的温度下，在声速中也观察到了明显的磁场滞后效应，表明存在磁场诱导的相变。在衰减的温度依赖性中，我们观察到与通常与弛豫效应相关的最大值明显不同的异常。它们归因于由于畴壁和连续变化的声速引起的色散效应的组合。总共揭示和分析了六种不同的磁相，包括在不同温度和磁场下的新型高磁场相。
