Ferromagnetism in lithium holmium fluoride-LiHoF4. II. Optical and spectroscopic measurements

Abstract

For pt.I see ibid., vol.8, p.4083 (1975). The absorption spectrum of LiHoF₄ has been studied, and the lowest-lying crystal-field levels of Ho³⁺ in LiHoF₄ have been determined. The ground state is a crystal-field doublet with a uniaxial g-factor of g_c=13.8+or-0.5. The spectroscopic measurements and the direct optical observation of domain structure both indicate that LiHoF₄ orders ferromagnetically parallel to the crystallographic c-axis at T_c=1.52+or-0.01K. The ordering is caused by magnetic dipole interaction, and the formation of domains of small demagnetizing factor is essential.