Study on Quantum Phase Transition of Magnetic Materials induced by Very High Field

在这项研究中，我们研制了磁体系统，按通常的方式进行了高达70T的磁化强度测量，并成功地观测到了由极强磁场引起的各种量子现象。例如，我们成功地观察到了被认为是S=1反铁磁自旋梯形材料的BLP-Teno的全EL/4平台。由于这种材料的磁性来自自由基团，自旋应该是1/2，但自旋之间存在很大的铁磁相互作用，导致两个自旋形成自旋1。从晶体结构分析，自旋1形成自旋梯形，从低场下的磁测量发现，自旋1之间的相互作用是反铁磁性的。到目前为止，高场磁化测量表明，1/4平台在44T左右开始，但该系统中1/4平台的存在并不明显。在我们的研究中，通过将磁化强度测量扩展到70T，第一次观察到了1/4平台的结束，这也允许我们看到整个平台区，开始于44T左右，结束于65T左右。另一个引人注目的例子是S=1。最近，人们已经清楚地看到，当分子吸附到一些铜化合物的微孔中时，其磁性以不同于反铁磁有序的方式消失。通过施加高场，我们成功地观察到了非磁态向磁态的转变。有趣的是，虽然S=1分子在材料中形成了自旋梯，但没有平台。

We have developed in this study the magnet system to carry out the magnetization measurement up to 70 T as a usual manner and succeeded in observing various quantum phenomena induced by very high magnetic field. For example, we have succeeded in observation of wholel/4 plateau in BlP-TENO, which has been regarded as an S=1 antiferromagnetic spin ladder material. As the magnetism of this material comes from free radical, spin should be 1/2 but there is large ferromagnetic interaction between the spins that makes two spins resulted spin 1. From a crystal structure analysis, spin 1 form a spin ladder and the interaction between spin 1 is found to be antiferromagnetic from the magnetic measurements at low field. Up to now, high field magnetization measurement has showed that 1/4 plateau begins around 44 T but it is not obvious that the 1/4 plateau exists in this system. The end of 1/4 plateau has been observed for the first time in our study by extending the magnetization measurement up to 70 T and it also allow us to see the whole plateau region, which begins around 44 T and ends around 65 T. Another striking example is a of S=1. Recently, it has become clear that magnetism of the molecule disappears in a different manner as the antiferromagnetic ordering when it is adsorbed into micro-pores of some copper complex materials. We have succeeded in observation of transition from non-magnetic state to magnetic one by applying high field. It is also interesting point that there is no plateau though the S=1 molecules form spin ladder in the materials.