Magnetic properties of the ferrimagnetic spinels systems CoFe2–2xCr2xO4

The magnetic properties of a diluted ferrimagnetic spinels system CoFe2–2xCr2xO4 are studied using the high-temperature series expansions method in the range 0 ≤ x ≤ 1. The inter-sublattice exchange interactions (JCo Cr or JCo–Fe) are calculated using the probability law. The high-temperature series expansions, together with the Padé-approximants method, are applied to the spinels systems CoFe2–2xCr2xO4 to determine the magnetic phase diagram, i.e., TC versus dilution x. The critical exponent associated with the magnetic susceptibility (γ) is deduced. PACS Nos.: 75.30.Et; 75.40.Cx; 74.25.Ha, 75.30.Cr

Magnetoelasticity and the spin rotation transition in cobalt

We study the spin reorientation process in cobalt using capacitance dilatometric measurements of the strain along the a- and c-axes of a single crystal and then apply a phenomenological theory of magnetostrictive interactions together with a theory of spin reorientation. We find no evidence of singularities in the behaviour at either of the temperatures at the beginning and end of this process. We calculate the temperature dependence of the magnetoelastic fourth-order single-ion anisotropy coefficient K4, and draw attention to the importance of higher order terms in the anisotropy. PACS Nos.: 74.25.Ha, 75.30.Gw, 75.50.Cc, 75.80.+q