Magnetic properties of (rare earth)Al₂intermetallic compounds

Magnetic properties of single-crystalDyAl2

“…This slight difference in Curie temperatures from the two different measurements is consistent with the variation of Curie temperatures reported in literature for the various types of measurements. 10 For the ͓100͔ and ͓110͔ single crystals, the amplitudes and the shapes of the ac Ј curves are somewhat similar and they resemble that of polycrystalline DyAl 2 ͑Ref. 14͒ with a slight bump at ϳ35 K which is due to the spin reorientation process.…”

“…On the contrary, for the ͓111͔ and ͓110͔ directions, the peaks observed near 35 K are related to the spin reorientation and the temperatures are in agreement with literature. [10][11][12] The magnetization curves for ͓111͔ and ͓110͔ are similar in shape and in absolute value, although the curve for ͓110͔ has slightly higher saturation values. The saturation value for ͓100͔ is significantly larger than in ͓110͔ and ͓111͔.…”

“…where B 0 is the applied field, M n is the magnetization calculated using an extended Bak model, 10,16 and is the exchange parameter. The cosines are the direction cosines for the three main directions in the crystal.…”

“…The cosines are the direction cosines for the three main directions in the crystal. The CEF parameters B 4 and B 6 were taken from Purwins and Leson, 10 i.e., B 4 =−͑5.5± 1.2͒ ϫ 10 −5 meV and B 6 =−͑5.6± 0.8͒ ϫ 10 −7 meV. These values were used to calculate MCE along the ͓100͔ and ͓110͔ directions, but for the ͓111͔ direction B 4 was reduced about 0.4% to −5.52ϫ 10 −5 meV in order to get agreement between the observed and calculated T C .…”

“…This compound has been extensively studied both theoretically and experimentally. 8,[10][11][12][13] At low temperature, the easy magnetization axis is the ͓100͔ direction, which changes to the ͓111͔ direction at ϳ40 K in zero magnetic field [10][11][12] or in an applied field of 57 kOe at 4 K. 10 A recent theoretical analysis 8 indicates that DyAl 2 should exhibit an anomaly in its ⌬S M vs. T curve, i.e., a negative MCE along the ͓111͔ direction below ϳ50 K. The anomaly was said to be associated with the change in the easy magnetization direction from the ͓100͔ to the ͓111͔. As reported by Levin et al, 14 the ac magnetic susceptibility of the polycrystalline DyAl 2 exhibits an anomaly at 42 K. In general, ac-susceptibility measurements are quite sensitive to detecting magnetic phase transitions initiated by a change of the magnetocrystalline anisotropy energy.…”