Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 40: Poster Session Correlated Electrons
TT 40.19: Poster
Wednesday, March 13, 2013, 15:00–19:00, Poster D
Magnetic cooling through quantum criticality — •Stefan Doerschug, Bernd Wolf, Natalia van Well, Franz Ritter, Robert Schindler, Wolf Assmus, and Michael Lang — Physikalisches Institut, Goethe-UniversitätFrankfurt (M), Germany
Close to a magnetic field-induced quantum-critical point the entropy at finite temperature exhibit a strong variation upon changing the magnetic field. We demonstrate that this accumulation of entropy can be used for realizing an efficient magnetic cooling. Our proof-of-principle demonstration is based on measurements and theoretical calculations of the magnetothermal properties of low-dimensional antiferromagnets close to their field-induced quantum-critical points. Here we present results of the magnetocaloric effect ΓB = T−1 (Δ T/ Δ B)S of different xy-antiferromagnets as a function of both field and temperature in the vicinity of the quantum-critical point and discuss various performance characteristics, such as the range of operation, efficiency and hold time. The corresponding figures of the quantum critical systems are compared with those of a state-of-the-art paramagnetic coolant. In addition, we present the experimental set-up, which is used to determine the magnetocaloric effect. The focus is particularly on the construction of a sample-holder for high-resolution measurements in the temperature range 0.02 K < T < 2 K.