Schottky anomaly

(solid-state physics) A contribution to the heat capacity of a solid arising from the thermal population of discrete energy levels as the temperature is raised; the effect is particularly prominent at low temperatures.

A contribution to the heat capacity of a solid arising from the thermal population of discrete energy levels as the temperature is raised. The effect is particularly prominent at low temperatures, where other contributions to the heat capacity are generally small. See also Specific heat.

Discrete energy levels may arise from a variety of causes, including the removal of orbital or spin degeneracy by magnetic fields, crystalline electric fields, and spin orbit coupling, or from the magnetic hyperfine interaction. Such effects commonly occur in paramagnetic ions. See also Low-temperature thermometry.

Corresponding to the Schottky heat capacity, there is a contribution to the entropy. This can act as a barrier to the attainment of low temperatures if the substance is to be cooled either by adiabatic demagnetization or by contact with another cooled substance. Conversely, a substance with a Schottky anomaly can be used as a heat sink in experiments at low temperatures (generally below 1 K or −457.9°F) to reduce temperature changes resulting from the influx or generation of heat. See also Adiabatic demagnetization; Low-temperature physics.