ABSORPTION-SPECTRA AND ZEEMAN EFFECT OF THE TRIVALENT HOLMIUM ION IN COMPOUNDS WITH TETRAGONAL ZIRCON STRUCTURE .3. HOPO4

For pt.II see ibid., vol.2, p.4701 (1990). The optical absorption spectrum of the transitions 5I8 to 3K7 and 5I8 to 3H6 of Ho3+ in HoPO4 and its Zeeman effect in magnetic fields along the crystal c axis were studied at temperatures below 5 K. The quantum numbers mu of the excited terms 3K7 and 3H6 were determined using linearly and circularly polarised transitions from the ground state. A short comparison of the experimental results for Ho3+ in (Ho0.1,Y0.9)VO4, (Ho0.1,Y 0.9)AsO4 and HoPO4 shows striking similarities but also remarkable differences.