High field induced magnetic anisotropy of Al-substituted erbium iron garnet single crystals

Magnetic properties of garnet single crystals Er3Fe5-zAlzO12 (z = 0.35 and 0.55) are reported under high magnetic field up to 230 kOe in the 4 K-300 K temperature range. The compensation temperature T-comp is shifted to highe r temperature for increasing Al content: T-comp = 80 K, 125 K and 152 K for z = 0, 0.35 and 0.55 respectively. In the spontaneous state, the magnetic anisotropy is at most 5% in the 4 K-30 K temperature zone and weaker or abs ent at higher temperatures. [100] remains the "easy" axis for both Al conte nts. Using the Dionne-refined Mel model of ferrimagnetic garnets with Al3ions located in tetrahedral sites, the calculated temperature dependences o f the spontaneous magnetization are in good agreement with experimental val ues. The strongly field dependent magnetic anisotropy of the garnets is imp ortant (up to 20%) only at low temperature (T < 50 K). For both AI contents , the magnetic field stabilizes [100] as the "easy" axis. Furthermore, when H < 30 kOe, Al substitution enhances [100] as the "easy" axis as compared to pure ErIG. Below T-comp in the high magnetic field zone (H > 150 kOe), t he onset of the usual canted magnetic phase takes place for H applied paral lel to the [111] crystallographic axis.