Structural and magnetic properties of Mn3O4 films grown on MgO(001) substrates by plasma-assisted MBE

Mn3O4 thin films with distorted spinel structure are grown on MgO(0 0 1) substrates by plasma-assisted molecular beam epitaxy (MBE) The films are (0 0 1) oriented and the lattice parameters are a = b approximate to 5.72 Angstrom, and c approximate to 9.5 Angstrom, with c/a = 1.66 slightly larger than the ratio of 1.64 for bulk single-crystal samples, if a body-center tetragonal unit cell is adopted for Mn3O4. It is found that the Curie temperature T-CF of the Mn3O4 film is 46 K higher than (T-CB = 42 K) for bulk single-crystal samples. The spontaneous magnetization reaches 1.73 mu(B)/molecule which is in between the reported results of 1.56 mu(B)/molecule for polycrystalline and 1.85 mu(B)/molecule for single-crystal sample. The temperature dependence of the inverse magnetic susceptibility in the paramagnetic range agrees well with the Curie-Weiss formula. The induced effective magnetic moment for Mn ion is about 3.59 mu(B), which is small compared with the 5.24 mu(B)/magnetic atom calculated based on electronic spins only. (C) 2000 Elsevier Science B.V. All rights reserved.