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TT: Fachverband Tiefe Temperaturen
TT 44: Poster Session Correlated Electrons
TT 44.59: Poster
Donnerstag, 17. März 2011, 10:00–13:00, P1
Quantitative measurement of low temperature magnetisation by a caloric technique — •Hanjo Ryll1,2, Klaus Kiefer1, Christian Rüegg3, Simon Ward3, Karl Krämer4, and Tobias Müller5 — 1Helmholtz-Zentrum Berlin für Materialien und Energie, Germany — 2Technische Universität Berlin, Germany — 3London Centre for Nanotechnology and Department of Physics and Astronomy, Great Britain — 4Universität Bern, Switzerland — 5Universität Kassel, Germany
Measurements of absolute magnetisation at very low temperatures and in high magnetic fields are notoriously difficult. The magnetocaloric effect (MCE) offers an alternative approach, which is applicable down to the mK temperature range. A quantitative MCE measurement is performed by precisely determining the temperature difference between sample and thermal bath with a well known thermal resistivity between bath and calorimeter. This allows for the measurement of the heat (δ Q) generated or absorbed by the sample for a changing field (δ B). Using Maxwell’s relations, the MCE yields the derivative of magnetisation with respect to temperature: (δ Q/δ B)/T = −(∂ M/∂ T)|B. Integration directly provides the uniform magnetisation M(B,T). The necessary integration constant is obtained by a magnetisation measurement at higher temperatures, for example by a vibrating sample magnetometer (VSM). The method was applied to the metal-organic spin ladder material (C5H12N)2CuCl4. Magnetisation and MCE data between 0.3 K and 3 K are shown as an example, together with quantitative modeling of these quantities for a perfect spin ladder.