Monopole heat transport and anomalous hysteresis effects in spin ice

Date

Apr 12, 2013

Time

2:00 PM - 3:00 PM

Speaker

Dr. Thomas Lorenz

Affiliation

Universität zu Köln

Language

en

Main Topic

Materialien

Other Topics

Materialien, Physik

Host

Kerstin Höllerer

Description

Elementary excitations in the spin-ice compound Dy_2Ti_2O_7 can be described as magnetic monopoles propagating independently within the pyrochlore lattice of magnetic Dy ions. In this talk, I will report heat-transport measurements to clarify the influence of the monopole excitations on the total thermal conductivity. From the anisotropic magnetic-field dependence and by additional measurements on reference compounds, we are able to separate the phononic and the magnetic contributions to the total heat transport, which both depend on the magnetic field. The field dependent phononic contribution arises from lattice distortions due to magnetic-field induced torques on the non-collinear magnetic moments of the Dy ions. For the magnetic contribution, we observe a highly anisotropic magnetic-field dependence, which correlates with the corresponding magnetization data reflecting the different magnetic-field induced spin-ice ground states. This anisotropic field dependence as well as various hysteresis effects suggest that the magnetic heat transport is essentially determined by the mobility of the magnetic monopole excitations in spin ice. In addition, we observe pronounced relaxation phenonema in the thermal conductivity, the specific heat and the magnetization. With decreasing temperature, these relaxation effects strongly increase and may even extend over hours at the lowest temperatures.

Links

• Seminars at the IFW

Last modified: Apr 12, 2013, 9:38:26 AM