Regensburg 2022 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 21: Correlated Electrons: Poster Session
TT 21.14: Poster
Mittwoch, 7. September 2022, 15:00–18:00, P1
Magnetic properties of monocrystalline euchroite Cu2(AsO4)(OH)3(H2O) — •Yannis Hilgers, Leonie Heinze, Dirk Menzel, and Stefan Süllow — IPKM, TU Braunschweig, Braunschweig, Germany
Previous studies of magnetic susceptibility and magnetisation on a natural polycrystalline sample of euchroite (Cu2(AsO4)(OH)3(H2O)) suggested that euchroite may be understood as a representation of a delta spin chain and exhibits a spin gap of about 50 K. In order to test this notion, we have performed a corresponding study on a monocrystalline sample, determining these properties along the three crystallographic axes. Magnetic susceptibility from 2 K to 300 K and magnetisation for magnetic fields up to 5 T were measured on a natural monocrystalline sample, previously characterized for crystallinity by Laue diffraction, of euchroite. From our data, we establish Curie-Weiss temperatures ΘCW,a = -150(20) K, ΘCW,b = -140(10) K, ΘCW,c = -140(10) K, significantly larger in value than ΘCW = -50 K by Kikuchi et al. Moreover, we find that at low temperatures, magnetic susceptibility exhibits a spin gap, and a residual magnetisation at low temperatures can be understood in terms of about 1 % free magnetic impurity (S = 1/2) moments. Fitting a Brillouin-function to the magnetisation data with S = 1/2 results in saturation magnetisations of Ms,a = 89,2(2,1) emu mol-1, Ms,b = 94,0(1,7) emu mol-1, Ms,c = 108,2(5,8) emu mol-1. From this, the minimal length lmin of the delta spin chain segments can be estimated to lmin = 350(50) Å. Altogether, our data are consistent with euchroite as a delta spin chain material with a spin gap of about 50 K.