MAGNETIC STRUCTURE OF AUMN

The results are reported of room-temperature magnetic torsion measurements on a single crystal of the t1 phase of the tetragonal, antiferromagnetic compound AuMn. It is found that the magnetic torsion resulting from an external field is dependent on the displacement of domain walls. The domain walls are assumed to result from localized pinning of the magnetization at random sites throughout the crystal. The torsion measurements are consistent with a magnetic structure in which the Mn magnetic moments align ferromagnetically in a-a planes, with adjacent planes antiferromagnetically aligned. The sublattice magnetization is found to lie along an a-axis. A uniaxial anisotropy field Ha1 = 39,800 Oe favoring alignment of the spin direction in the a-a plane is calculated from classical dipolar interactions. The torsion measurements indicate that the in-plane anisotropy field HA2 stabilizing the magnetization direction against rotation in the a-a plane is larger than 120 Oe. The roomtemperature susceptibility difference χ⊥ -χ∥is found to be approximately 9·5 × 10-5. © 1968.