Programme

P.91 -- Posters, VCTP-51

Date: Thursday, 6 August 2026

Time: 09:30 - 10:30

Magnetocaloric effect in the skyrmion material Cu$_2$OSeO$_3$

T. L. Phan, B. D. Tu, and H. N. Nhat*

Faculty of Physics Engineering and Nanotechnology, VNU University of Engineering and Technology, Vietnam National University, Xuan Thuy road, Cau Giay, Hanoi, Vietnam

Polycrystalline Cu$_2$OSeO$_3$ with the cubic structure has been prepared by solid-state reactions. Magnetization measurements indicate its magnetic ordering established at temperatures below T$_\mathrm{C}$ of ~59 K. At low fields H < 500 Oe, zero-field-cooled and field-cooled M(T) curves show a sharp peak at ~57 K associated with the skyrmion phase, and the splitting between them, which become invisible at higher fields. Both Maxwell's relations and mean-field theory have been used to calculate the magnetic-entropy change. The results indicate the maximum magnetic-entropy change near T$_\mathrm{C}$, which is about 5.7 J/kgK for a field variation of 140 kOe. For the first time, direct measurements of the adiabatic-temperature change (delT) for Cu$_2$OSeO$_3$ have been carried out, indicating its significant variation in value. At temperatures around T$_\mathrm{C}$, delT reaches about 2.6 K for the field H = 140 kOe. At the same field, the relative cooling power and working range for refrigeration applications are about 222 J/kg and 40 K, respectively. Additional analyses of magnetocaloric-effect-related exponents under high applied fields, we have found that Cu$_2$OSeO$_3$ exhibits short-range magnetic ordering, which is ascribed to a coexistence of ferromagnetic and antiferromagnetic interactions between Cu ions at different sublattices.

Presenter: Hoang Nam Nhat