MAGNETIC TRANSITION AND COERCIVITY IN TBMN6SN6

In the present paper, the structure and magnetic properties of TbMn6Sn 6 have been investigated. TbMn6Sn6 is found to be of HfFe6Ge6-type str ucture (space group P6/mmm) with a = 5.5461 Angstrom, c = 9.0477 A and V = 241 Angstrom(3). This compound shows ferrimagnetic behaviour with the ordering temperature T-c = 421 K. A peak is also observed in the thermal magnetic curve at 330 K. Under magnetic fields of 100, 300 and 400 Oe, the magnetization values first increase with increasing tempe rature, next exhibit a peak and then decrease with further increase in temperature. When the applied magnetic field is sufficiently large, e .g. 1000 and 2100 Oe, the magnetization of the whole sample decreases with increasing temperature. With increasing temperature from the rang e 77-300 K, the coercivity first increases, next undergoes a peak at a bout 200 K and then decreases. At room temperature a magnetization jum p is observed in the magnetization curves at a field of about 4 kOe in both the aligned and the free powder samples. This jump may be attrib uted to the spin-flop or metamagnetic transition. The magnetic anisotr opy field at room temperature is found to be 8.33 kOe.