Rudra Sekhar Manna, Bernd Wolf, Mariano de Souza, Michael Lang
We report on the realization of a capacitive dilatometer, designed for high-resolution measurements of length changes of a material for temperatures 1.4\,K $\leq T \leq$ 300\,K and hydrostatic pressure $P \leq$ 250\,MPa. Helium ($^4$He) is used as a pressure-transmitting medium, ensuring hydrostatic-pressure conditions. Special emphasis has been given to guarantee, to a good approximation, constant-pressure conditions during temperature sweeps. The performance of the dilatometer is demonstrated by measurements of the coefficient of thermal expansion at pressures $P \simeq$ 0.1\,MPa (ambient pressure) and 104\,MPa on a single crystal of azurite, Cu$_3$(CO$_3$)$_2$(OH)$_2$, a quasi-one-dimensional spin S = 1/2 Heisenberg antiferromagnet. The results indicate a strong effect of pressure on the magnetic interactions in this system.
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http://arxiv.org/abs/1206.2882
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