NMR Study of Transferred Hyperfine and Exchange Interactions in Ferromagnetic Semiconductor EuLiH₃

Abstract

The zero field ¹⁵³Eu, ³Li and ¹H NMR in a cubic perovskite ferromagnet EuLiH₃ (T_c=37 K) have been observed as functions of temperature and pressure. The ¹⁵³Eu and ⁷Li NMR frequencies are 123.4 and 7.95 MHz at 4.2 K, respectively, corresponding to the effective fields H_i=−266.4 and +4.80 kOe, and a broad ¹H NMR is observed in the frequency range between 20 and 46 MHz. The nearest neighbour exchange constant of J₁=0.83 K is obtained by fitting ¹⁵³ν(T) to the spin wave theory. The transferred hyperfine (thf) field at Eu nuclei is derived as H₁=+5.2 kOe per n.n. Eu²⁺ ion by estimating the core polarization field from the hyperfine splitting of the Eu²⁺ ESR in diamagnetic SrLiH₃. The pressure dependence of ∂H_i⁄∂P=0.246 kOe/kbar for ¹⁵³Eu is attributed to an increase of H₁ under pressure.