High-field magnetization and magnetic phase diagrams for three symmetry axes in single-crystal CeAl₂

We measured high-field magnetization, up to 56 T, in CeAl2 crystallized in MgCu2-type cubic structure, using a pulse magnet. We observed the conventional metamagnetic transition from antiferromagnetism to field-induced ferromagnetism near 5 T. Magnetic phase diagrams were determined for the (100), (110), and (111) axes using high quality single crystals, as identified by the detection of the de Haas-van Alphen oscillation. As reported in previous research with polycrystalline samples for mapping the magnetic phase diagram of CeAl2, two phase boundaries were observed within the antiferromagnetic phase. This structure of the magnetic phase diagram is similar to that of centrosymmetric skyrmion system such as GdRu2Si2, in which the Ruderman-Kittel- Kasuya-Yosida interaction plays an important role. Our measurements using single crystals revealed that phase boundaries within the antiferromagnetic phase varied depending on magnetic field direction. For magnetization along (100), a weak, broad shoulder was observed that reached to approximately 15 K, far higher than the 4 K Neel temperature. This single-crystal study resolves the detailed magnetic phase diagrams to three symmetry axes. Mapping the orientation-dependent magnetic phase diagrams supports the magnetic structure determination for each phase and each symmetry axis. The newly mapped orientation-dependent magnetic phase diagrams provide insights that clarify underlying magnetic correlation and plausible skyrmion phase in heavy fermion compound CeAl2.