Neutron and Magnetic Studies of a Single Crystal of Fe₂TiO₄

Abstract

Magnetic properties of a single crystal of almost pure Ulvöspinel Fe_2.05Ti_0.95O_4.00 have been investigated by neutron diffraction and magnetic studies. Fe₂TiO₄ is a perfect inverse spinel with oxygen parameter of u=0.386±0.001 at room temperature. The crystal becomes weakly ferromagnetic below 142°K. The magnetic structure is of the Néel type with the sublattice magnetic moments of 4.2±0.2μ_B on both octahedral and tetrahedral sites at 4.2°K. The moment on the octahedral site decreases with increasing temperature faster than that on the tetrahedral site. The spontaneous weak ferromagnetic moment is induced in one of the ⟨100⟩ direction perpendicular to spins. The spins tend to orient to the direction of the field, only when the magnetic field is applied in the [100] direction. The crystal is suggested to distort tetragonally at low temperatures with the spin along the long axis. The average \baru parameter at 4.2°K is also 0.386±0.001.