Magnetostriction anomalies in DyPO4 caused by interaction of levels

Anomalies of the linear magnetostriction caused by the interaction of energ y levels of the rare-earth ion in DyPO4 in a strong magnetic field along th e [100] and [110] axes are investigated both experimentally and theoretical ly. Smeared jumps and maxima on the magnetostriction curve lambda (H) and i ts derivative d lambda (H)/dH along the three perpendicular axes in the cri tical fields H-c = 140 and 200 kOe, when the lower energy levels of the Dy3 + ion converge, are discovered. Under the assumption of the adiabatic chara cter of the magnetization process in pulsed fields, the quadrupole moments <O-2(0)>, <O-2(2)>, and <P-x y> are calculated, which give a rather accurat e description of the anisotropy of the linear magnetostriction lambda (H) a nd its dependence on temperature and magnetic field. It is discovered that a jumplike variation of the quadrupole interaction of alpha and gamma(delta ) symmetry in DyPO4 under crossover leads, according to the experiment, to the decrease of the critical field by about 20 kOe and a sharper change of the linear magnetostriction lambda (H) and its derivative d lambda (H)/dH i n the vicinity of the crossover. (C) 2001 MAIK "Nauka/Interperiodica".