Development and characterization of a microcalorimeter based on a Si-N membrane for measuring a small specific heat with submicro-joule precision

We report on development of a silicon-nitride-based microcalorimeter for measuring the heat capacity of a small single crystal or films over a wide temperature range and under high magnetic fields. The fabricated calorimeter is adapted to a commercial cryostat equipped with a 9 T magnet (Quantum Design, PPMS™) and is operated by using a custom-made program based on a thermal relaxation method considering two relaxation times. The measured heat capacity data for Cu are consistent with the literature values within ∼20 % in a temperature range between 20 and 300 K. Measurements of a flux-grown LuMnO ₃ single crystal of ∼300 μg exhibit large residual entropy below its Néel temperature, which seems to be a common feature in the hexagonal RMnO ₃ (R = rare earth) system.