NMR Study of Weak Antiferromagnetism in NbFe₂

Abstract

The ⁹³Nb NMR and magnetization have been measured to investigate the nature of weak antiferromagnetism in the hexagonal C-14 Laves phase compound, NbFe₂. The temperature and magnetic field dependence of the magnetization and nuclear spin-lattice relaxation time, T₁, confirmed that an antiferromagnetic transition occurs at low fields and is easily suppressed by fields above 6 kOe. An analysis of T₁ shows that both the ferro- and antiferromagnetic spin fluctuations coexist in this system and that the ferromagnetic component is dominant at high fields. The coexistence of two components of the spin fluctuation may be related to the anomalous temperature dependence of the magnetic susceptibility at high temperatures. The analysis of NMR spectra suggests that the magnetic structure at the ordered state is of the spin density wave type giving rise to a large distribution of hyperfine field.