Accession Number : AD0865747

Title :   Effect of Range of Dipole-Dipole Interaction on the Anisotropy in the MnF2 Paramagnetic Susceptibilities,

Corporate Author : NAVAL ORDNANCE LAB WHITE OAK MD

Personal Author(s) : Libelo, Louis F. ; Kligman, Ronald L. ; Tanaka, Tomoyasu

Report Date : 09 JAN 1970

Pagination or Media Count : 37

Abstract : The high temperature behavior of the anisotropy in the magnetic susceptibility of single crystal MnF2 has been investigated in the two-spin correlation limit of the self-consistent cluster variation theory. Earlier measurements showed a maximum occurs for this anisotropy at about 120 degrees K and the usual failing off with increasing temperature thereafter. In addition to this characteristic the measurements indicated the occurrence of zero anisotropy considerably above the critical temperature. The temperature dependence of the anisotropy is calculated using a Heisenberg spin Hamiltonian and including explicit dipole-dipole interaction out to ninth neighbors. This accounts for correlation of each spin with sixty neighboring spins. The results indicate that a maximum in the anisotropy could occur above the phase transition temperature. However, it will have to occur very close to that point. Furthermore, it was found that the zero in the anisotropy does not occur above the critical temperature. The findings are in accord with recent NMR measurements of MnF2. (Author)

Descriptors :   (*MANGANESE COMPOUNDS, MAGNETIC PROPERTIES), (*MAGNETIC MOMENTS, INTERACTIONS), PARAMAGNETIC MATERIALS, ANTIFERROMAGNETISM, SINGLE CRYSTALS, ANISOTROPY, FLUORIDES.

Subject Categories : Electricity and Magnetism
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE