Neutron and Magnetic Studies of a Single Crystal of Fe₂TiO₄

Abstract

Magnetic properties of a single crystal of almost pure Ulvöspinel Fe 2.05 Ti 0.95 O 4.00 have been investigated by neutron diffraction and magnetic studies. Fe 2 TiO 4 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 \bar u parameter at 4.2°K is also 0.386±0.001.