Магнитострикция гексагональных монокристаллов HoMnO-=SUB=-3-=/SUB=- и YMnO-=SUB=-3-=/SUB=-

We report on the magnetostriction of hexagonal HoMnO_3 and YMnO_3 single crystals in a wide range of applied magnetic fields (up to H = 14 T) at all possible combinations of the mutual orientations of magnetic field H and magnetostriction Δ L/L . The measured Δ L/L ( H, T ) data agree well with the magnetic phase diagram of the HoMnO_3 single crystal reported previously by other authors. It is shown that the nonmonotonic behavior of magnetostriction of the HoMnO_3 crystal is caused by the Ho^3+ ion; the magnetic moment of the Mn^3+ ion parallel to the hexagonal crystal axis. The anomalies established from the magnetostriction measurements of HoMnO_3 are consistent with the phase diagram of these compounds. For the isostructural YMnO_3 single crystal with a nonmagnetic rare-earth ion, the Δ L/L ( H, T ) dependences are described well by a conventional quadratic law in a wide temperature range (4–100 K). In addition, the magnetostriction effect is qualitatively estimated with regard to the effect of the crystal electric field on the holmium ion.

A highly selective and sensitive turn-on fluorescent probe for the detection of holmium ion and its bioimaging

The phenolphthalein aldehyde was synthesized and used to a turn-on fluorescent probe for the detection of holmium ion (Ho3+) in HEPES : DMF = 1 : 1 (v/v pH = 7.4) solution with an excellent selectivity and sensitivity for Ho3+over other metal ions.

Composition-Dependent Ultraviolet up-Conversion Luminescence in Yb3+-Ho3+ Co-Doped Germanium- Phosphate Glasses

Yb3+-Ho3+ co-doped germanium-phosphate glasses have been prepared and characterized for its optical properties through measuring photoluminescence and Raman spectra. UV-visible up-conversion emission of holmium ion in Yb3+-Ho3+ co-doped germanium-phosphate glasses has been observed on 980nm excitation. As phosphate was substituted for germanium the red emission Red I decreased at first and then increased later while the green emission Green I decreased and the ratio of Red I to Green I increased. Interestingly, the value of ultraviolet emission intensity was larger than that of the blue and green emission intensity in phosphate glass sample. We believe that Yb3+-Ho3+ co-doped germanium-phosphate glasses might be a potential host material for developing ultraviolet all–solid compact lasers. The possible excitation mechanisms involved in these emissions were discussed, too.

Thermal and magnetic properties of barium holmium fluoride, BaHo 2 F 8

Single crystals of barium holmium fluoride, BaHo 2 F 8 , have been grown by the Czochralski technique, and the monoclinic crystal structure has been confirmed by using X-ray diffraction. The trivalent holmium ion Ho 3+ , 4f 10 , 5 I 8 , has a single stable isotope 165 Ho, with I = 7/2. The crystalline electric field at the lanthanide site has low symmetry, and previous measurements on the dilute compound Ba(Y 0.99 Ho 0.01 ) 2 F 8 have shown that the ground state of the holmium ion is a non-Kramers doublet with a purely Ising-like g value. In the present work, the stoichiometric compound BaHo 2 F 8 has been studied by optical spectroscopy, together with measurements of the heat capacity, magnetic susceptibility and magnetic moment. The results show that BaHo 2 F 8 enters an antiferromagnetically ordered state below T N = 1.76 K. The principal direction of the holmium moments is the crystallographic a -axis, for which group theoretical considerations limit the possibilities for antiferromagnetic order to their configurations. In the optical absorption spectrum between 4.2 K and T N , shifts in the spectral lines of the holmium ion indicate the presence of short-range magnetic order. This is implied also by the fact that some 40% of the magnetic entropy is contained in the heat capacity at temperatures above T N . Purely magnetic dipolar interactions would give an ordering temperature of 0.1 K, much less than the observed value of T N . Dipolar interaction therefore plays only a minor role in the magnetic behaviour; antiferromagnetic exchange interaction is dominant.