Alexander M. Donald | Searcharxiv

arXiv2026

Sub-10 mK "In-cell" Magnetic Refrigeration for Cryogen-free Cryostats

A design and implementation of "in-cell" magnetic refrigeration to achieve sub-10 mK temperatures T in cryogen-free dilution refrigerators is presented. The ultra low temperatures below 5 mK are attained in finite magnetic fields B up to 1 T. The holding time below 5 mK varies between about 3 to 30 hours, depending on the final magnetic field after demagnetization process. The developed technique can be used to study low dimensional devices at ultra low electron temperatures in the High B/T regime.

cond-mat.mtrl-sci↗

arXiv2026

Metastable MnBi$_2$Te$_4$ enabled by magnetic-field-assisted synthesis

Magnetic topological insulators provide a unique platform to explore the interplay between magnetism and topology. MnBi$_2$Te$_4$, known for its A-type antiferromagnetic (AFM) ground state, undergoes a striking transformation when single crystals are grown in an applied magnetic field. Despite retaining the same crystal structure, field-grown MnBi$_2$Te$_4$ exhibits a ferromagnetic (FM) ground state with a Curie temperature of $\sim$ 12.5 K, confirmed by magnetization, magnetic torque, electrical resistivity, and specific heat measurements. First-principles calculations support these findings, revealing that magnetic-field-assisted synthesis can effectively reconfigure the ground-state spin order and thereby modify the material's electronic properties, as reflected in the de Haas-van Alphen oscillation seen in the magnetic torque.

cond-mat.mtrl-sci↗