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Magnetic Ordering in HoAsO 4 Investigated by Means of Specific Heat and Spectroscopic Measurements
Author(s) -
Schwab M.,
Berkhahn W.,
Kahle H. G.,
Simon A.,
Wüchner W.
Publication year - 1974
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220650220
Subject(s) - antiferromagnetism , zeeman effect , condensed matter physics , paramagnetism , hyperfine structure , exchange interaction , magnetic moment , chemistry , anomaly (physics) , excited state , magnetic field , physics , atomic physics , ferromagnetism , quantum mechanics
The heat capacity, optical absorption spectrum, and Zeeman effect of HoAsO 4 have been measured at low temperatures. The specific heat shows a lambda anomaly at T N = = (0.557 ± 0.005) K which has to be attributed to a magnetic phase transition from the paramagnetic to the antiferromagnetic state. The anomaly is superimposed on a large contribution from the nuclear hyperfine interaction of holmium. Spectroscopic measurements indicate that the lowest lying crystal field state of the Ho 3+ ions in HoAsO 4 is a doublet Γ 5 ( g c = 15.3 ± 0.3) and that the first excited state is a singlet Γ 1 at about 7.5 cm −1 . The magnetic interaction in HoAsO 4 has the form of Ising interaction. A simple two sublattice structure with magnetic moment direction along the optical axis is proposed for the ordered state. Assuming this structure, an estimation of exchange interaction to nearest (nn), next nearest (nnn), and third nearest (tnn) neighbours was performed. It shows that the contributions to the total exchange field of the nn and nnn are nearly compensated by those of tnn. Dipole–dipole interaction was found to be dominant for the antiferromagnetic ordering in HoAsO 4 .