A comparative study of the magnetic properties of the 1/1 approximant Ag₅₀In₃₆Gd₁₄and the icosahedral quasicrystal Ag₅₀In₃₆Gd₁₄

Abstract

We report on measurements of the dc and ac magnetic susceptibility, (155)Gd Mössbauer spectra, and specific heat of the 1/1 approximant Ag(50)In(36)Gd(14), and of the ac magnetic susceptibility of the icosahedral quasicrystal Ag(50)In(36)Gd(14). These alloys are shown to be spin glasses. For the icosahedral quasicrystal Ag(50)In(36)Gd(14), 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 Ag(50)In(36)Gd(14) occurs in two stages: at T(f(1)) = 3.7 K, Gd spins develop short-range correlations but continue to fluctuate, and then long-range freezing is achieved at T(f(2)) = 2.4 K. The frequency dependences of T(f(1)) and T(f(2)) 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 (155)Gd Mössbauer spectra of the 1/1 approximant Ag(50)In(36)Gd(14) 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(f(1)), but the temperature derivative of the magnetic entropy peaks at T(f(1)). The Debye temperature of the 1/1 approximant Ag(50)In(36)Gd(14) is 199(1) K as determined from the Mössbauer data, and 205(2) K as determined from the specific heat data.

Antiferromagnetic order in the quasicrystal approximant Cd6Tb studied by x-ray resonant magnetic scattering

“…22 Furthermore, both the Ag-In-Gd icosahedral phase and its 1/1 cubic approximant show similar behavior as both evolve to spin-glasses at low temperature. 23 Surprisingly, the 1/1 approximant to the Cd-Mg-R icosahedral phases, Cd 6 R, appears to be an exception to the rule. In particular, recent magnetic susceptibility and specific heat measurements [24][25][26] indicate the onset of long-range magnetic order at low temperature.…”

Magnetic properties of icosahedral quasicrystals and their cubic approximants in the Cd–Mg–RE (RE = Gd, Tb, Dy, Ho, Er, and Tm) systems

“…The imaginary part 𝜒𝜒 ac ̋ in Figure 6b illustrates a sharp rise near Tf. Such a frequency dependent variation of the ꭕ ac ́ and 𝜒𝜒 ac ̋ offers a reliable criteria for distinguishing a spin-glass-like material from other magnetic systems [31,32]. Note that this is the first observation of the spin-glass-like feature in the cubic 2/1 and 1/1 ACs in the ternary Cd-Mg-RE systems.…”

Peritectic Formation and Phase Stability of the Icosahedral Quasicystal i-GdCd and Its Ternary Variants with Zn, Mg, and Y

“…In contrast, Zn substitution results in a significant contraction of lattice parameters (the metallic radius of Zn is 1.37 Å) which actually exceeds by far the contraction trend observed for RE-Cd when going from Gd to Tm. The lattice constant ( a ) of a 1/1 approximant to an i-QC is related to the six-dimensional hypercubic lattice constant ( a 6D ) of the i-QC via the relation: , where is the golden mean constant. , The calculated a 6D values of the present compounds are listed in Table together with their corresponding a ’s, which were obtained from standard PXRD analysis. In addition, due to the fact that the Gd–Cd–Zn system is an original system presented in this work, we further confirm its quasicrystallinity using selected area electron diffraction (SAED) experiment on the Gd 11 Cd 77 Zn 12 sample.…”

“…(1 5 )/2 τ = + is the golden mean constant. 17,18 The calculated a 6D values of the present compounds are listed in Table 2 together with their corresponding a's, which were obtained from standard PXRD analysis. In addition, due to the fact that the Gd−Cd−Zn system is an original system presented in this work, we further confirm its quasicrystallinity using selected area electron diffraction (SAED) experiment on the Gd 11 Cd 77 Zn 12 sample.…”