Long-range magnetic order in real icosahedral quasicrystals

Abstract

Quasicrystals (QCs), first discovered in 1984, generally do not exhibit long-range magnetic order. Here, we report on long-range magnetic order in the real icosahedral quasicrystals (i QCs) Au–Ga–Gd and Au–Ga–Tb. The Au65Ga20Gd15 i QC exhibits a ferromagnetic transition at TC = 23 K, manifested as a sharp anomaly in both magnetic-susceptibility and specific-heat measurements. Quick magnetic saturation to almost the full moment (7μB/Gd3+) is observed under 100 Oe at 2 K. This is the first observation of long-range magnetic order in a real quasicrystal, in contrast to the spin-glass-like behaviours observed for the other magnetic quasicrystals found to date. Moreover, when Gd is replaced by Tb, i.e. for the Au65Ga20Tb15 i QC, a ferromagnetic behaviour is still retained with TC = 16 K. Although the sharp anomaly in the specific heat observed for the Au65Ga20Gd15 i QC is significantly broadened upon Tb substitution, neutron-diffraction experiments clearly show the marked development of magnetic Bragg peaks below TC, indicating long-range magnetic order for the Au65Ga20Tb15 i QC also. Our findings can contribute to the further investigation of exotic magnetic orders formed on real quasiperiodic lattices with unprecedented highest global symmetry, i.e. icosahedral symmetry.

Magnetic dynamics of hedgehog in icosahedral quasicrystal

“…As for the QC, the spin-glass behavior has been observed in the QC Cd-R (R=Gd, Tb, Dy, Ho, Er, and Tm) 12 . Recently, the FM orders have been discovered in the QC Au 65 Ga 20 R 15 (R=Gd and Tb) 13 and in Au x Ga 85−x Dy 15 (x = 62-68) 14 , which have brought about the breakthrough.…”