A comparative study of the magnetic properties of the 1/1 approximant Ag50In36Gd14 and the icosahedral quasicrystal Ag50In36Gd14

作者：Wang P^*; Stadnik Z M; Al Qadi K; Przewoznik J

来源：Journal of Physics: Condensed Matter , 2009, 21(43): 436007.

DOI：10.1088/0953-8984/21/43/436007

We report on measurements of the dc and ac magnetic susceptibility, Gd-155 Mossbauer spectra, and specific heat of the 1/1 approximant Ag50In36Gd14, and of the ac magnetic susceptibility of the icosahedral quasicrystal Ag50In36Gd14. These alloys are shown to be spin glasses. For the icosahedral quasicrystal Ag50In36Gd14, spin freezing occurs at T-f = 4.3 K, and the frequency dependence of T-f is well accounted for by the Vogel-Fulcher and power laws. Spin freezing in the 1/1 approximant Ag50In36Gd14 occurs in two stages: at T-f1 = 3.7 K, Gd spins develop short-range correlations but continue to fluctuate, and then long-range freezing is achieved at T-f2 = 2.4 K. The frequency dependences of T-f1 and T-f2 can be accounted for by means of the Vogel-Fulcher law and the critical slowing down dynamics. It is shown that the spin freezing in both alloys is a nonequilibrium phenomenon rather than a true equilibrium phase transition. The Gd-155 Mossbauer spectra of the 1/1 approximant Ag50In36Gd14 confirm that the Gd spins are frozen at 1.5 K and are fluctuating at 4.6 K. The magnetic specific heat exhibits a maximum at a temperature that is 30% larger than T-f1, but the temperature derivative of the magnetic entropy peaks at T-f1. The Debye temperature of the 1/1 approximant Ag50In36Gd14 is 199(1) K as determined from the Mossbauer data, and 205(2) K as determined from the specific heat data.

• 出版日期2009-10-28