Apetrei A, Mirebeau I, Goncharenko I, Andreica D, Bonville P
Laboratoire Léon Brillouin, CEA-CNRS, CE-Saclay, 91191 Gif-sur-Yvette, France.
Phys Rev Lett. 2006 Nov 17;97(20):206401. doi: 10.1103/PhysRevLett.97.206401. Epub 2006 Nov 15.
We have studied (Tb1-xLax)2Mo2O7 pyrochlores by neutron diffraction and muSR at ambient and under applied pressure. (Tb,La) substitution expands the lattice and induces a change from a spin-glass-like state (x=0) to a noncollinear ferromagnet (x=0.2). In the ferromagnetic structure, the Tb moments orient close to their local anisotropy axes as for an ordered spin ice, while the Mo ones orient close to the net moment. The temperature dependence of the muSR relaxation rates and static local fields suggests a second transition of dynamical nature below the Curie transition. Under pressure, the long range order breaks down and a spin-glass-like state is recovered. The whole set of data provides a microscopic picture of the spin correlations and fluctuations in the region of the ferromagnetic-spin-glass threshold.
我们通过中子衍射和μ子自旋弛豫（muSR）技术，在常压和外加压力条件下对（Tb1-xLax）2Mo2O7焦绿石进行了研究。（Tb，La）替代使晶格膨胀，并引发从类自旋玻璃态（x = 0）到非共线铁磁体（x = 0.2）的转变。在铁磁结构中，Tb磁矩的取向接近其局部各向异性轴，如同有序自旋冰的情况，而Mo磁矩的取向则接近净磁矩。μ子自旋弛豫率和静态局部场的温度依赖性表明，在居里转变温度以下存在二级动力学转变。在压力作用下，长程有序被破坏，类自旋玻璃态得以恢复。这一系列数据提供了铁磁 - 自旋玻璃阈值区域内自旋关联和涨落的微观图像。
