TmZn: A possible regenerator material for low-temperature cryocoolers

The intermetallic compound TmZn has two low-temperature magnetic phase transitions and is a potential regenerator material. Application of a magnetic field to regulate the phase-transition temperature by influencing the specific heat $cp(T)$ dependence in TmZn was investigated. The low-temperature heat capacity of a monocrystalline TmZn sample was measured as a function of magnetic field (up to 30 kOe). The anisotropy of the transition temperature in the applied magnetic field was modeled using ac susceptibility measurements. From the measured values, the TmZn regenerator specific heat was calculated taking into account both the temperature regulation and the anisotropy. A numerical simulation study of the TmZn regenerator was made. The results show an improvement in TmZn regenerator performance by the application of a magnetic field and employment of the transition anisotropy. The minimal cold chamber temperature was lowered from 11.76 to 9.77 K by the application of a magnetic field of 30 kOe. The performance of the TmZn regenerator is compared with the existing regenerator materials, $Er3Ni$⁠, Pb, $HoCu2$⁠, and $Er50Pr50$⁠.