Direct Observation of the High Magnetic Field Effect on the Jahn-Teller State in TbVO4.

We report the first direct observation of the influence of high magnetic fields on the Jahn-Teller (JT) transition in TbVO(4). Contrary to spectroscopic and magnetic methods, x-ray diffraction directly measures the JT distortion; the splitting between the (311)/(131) and (202)/(022) pairs of Bragg reflections is proportional to the order parameter. Our experimental results are compared to mean-field calculations, taking into account all possible orientations of the grains relative to the applied field, and qualitative agreement is obtained.

Magnetic properties and the crystal field problem for tetragonal HoBa(2)Cu(3)O(x).

Magnetic susceptibilities of the first and third orders as well as the magnetization of the singlet paramagnet HoBa(2)Cu(3)O(x) (x≈6.0) at low temperatures are studied experimentally using a SQUID magnetometer and compared with theoretical calculations. The magnetic behaviour of single-crystal HoBa(2)Cu(3)O(x) at low temperature is found not to follow the one calculated on the basis of the known crystal field parameters.