Nuclear Magnetic Relaxation in the Metallic Localized Moment System Ir₂MnGa

Abstract

The nuclear spin-lattice relaxation time T₁ of ⁶⁹Ga and ⁷¹Ga in the antiferromagnetic Heusler alloy Ir₂MnGa has been measured in the paramagnetic state. The observed 1⁄T₁ for T>>T_N is explained quantitatively by the exchange-coupled localized moment fluctuations. This indicates that the correlation time of the paramagnetic spin fluctuations is well characterized by the exchange frequency of localized moments, in contrast to the case of the temperature-induced localized moments where the frequency spectrum of the fluctuations spreads over a much higher frequency.