CONTRIBUTION OF PT IMPURITIES TO SPIN CONFIGURATIONS IN THE REENTRANTSPIN-GLASS NIMN

We have measured the temperature-dependent linear and nonlinear suscep tibilities of the reentrant spin glass Ni100-xMnx (x = 22.4, 23.0 and 23.4) and Pt-doped samples Ni100-x-yPtyMnx(x = 23.5, y = 0.6 and 1.1) in order to elucidate the thermal evolution of spin configurations in the low-temperature states. The nonlinear susceptibility in the reentr ant spin glasses Ni77.0Mn23.0 and Ni76.6Mn23.4 shows a peak correspond ing to the appearance of the vortex-like spin structure in addition to conventional phase transitions. Such an extra peak becomes more prono unced in Ni75.9Pt0.6Mn23.5 and Ni75.4Pt1.1Mn23.5 with increasing Pt co ntent, suggesting the appearance of a long-range vortical spin arrange ment above the spin freezing temperature. In these Pt-doped samples, t he singularity due to the spin glass transition becomes indistinct and the ferromagnetic transition disappears. We explain this contribution of Pt to the spin configuration in terms of the enhanced magnetic ani sotropy due to a Dzyaloshinsky-Moriya-type interaction.