Dresden 2011 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 49: CE: Spin Systems and Itinerant Magnets 2

TT 49.15: Vortrag

Donnerstag, 17. März 2011, 18:00–18:15, HSZ 03

Vibrating coil magnetometry of the spin ice state in Ho₂Ti₂O₇ — •C. Krey¹, S. Legl¹, S. R. Dunsiger¹, C. Pfleiderer¹, J. S. Gardner², and J. Roper³ — ¹Physik Department E21, Technische Universität München, Germany — ²NIST, Center for Neutron Research, Gaithersburg, Maryland, USA — ³Los Alamos National Laboratory, Los Alamos, USA

The ’spin ice’ model highlights the strong analogy between spin ordering in Ising magnets and proton ordering in ice. Recently, it has been proposed that the excitations may be described in terms of magnetic point defects or emergent magnetic monopoles [1]. The cubic pyrochlore systems Dy₂Ti₂O₇ and Ho₂Ti₂O₇ are excellent experimental realizations of spin ice, where the local ⟨ 111⟩ Ising anisotropy of the rare earth sites in combination with net ferromagnetic interactions give rise to a highly degenerate ground state. The similarities with water ice are the observation of a first order transition terminating in a critical point in the magnetization of Dy₂Ti₂O₇ for applied magnetic fields along the global ⟨ 111⟩ direction. We report a comprehensive study of the magnetization at mK temperatures of Ho₂Ti₂O₇ by means of a vibrating coil magnetometer [2]. We observe considerable qualitative similarities with Dy₂Ti₂O₇ but also distinct differences. We consider the role of strong hyperfine interactions associated with Ho compounds.
Ryzhkin, J Exp and Theor Physics 101, 481 (2005), Castelnovo et al., Nature 451, 42 (2008)
Legl et al., Rev. Sci. Instrum. 81, 043911 (2010)