Spin-glass behavior in an antiferromagnetic frustrated spinel:ZnCr1.6Ga0.4

Abstract

A study of magnetic properties in the insulating spinel ZnCrl 6Gao 404 (chromium ions in octahedral sites) has been made by carrying out low-field dcand ac-susceptibility measurements as well as neutron diffraction, Mossbauer, and EPR experiments, which all give evidence of spin-glass-like behavior. The topological frustration, connected with the high ground-state degeneracy of the antiferromagnetic spinel octahedral sublattice, is the origin of the spin-glass ordering. Strong nearestneighbor antiferromagnetic interactions are dominant in the system, leading to short-range magnetic order which appears at temperatures much higher than the freezing temperature defined by the acsusceptibility cusp [T(v=17 Hz}=2.50 K is frequency dependent]. The thermoremanent magnetization does not vanish at Tf, suggesting the existence of uncompensated clusters blocked above Tf.A paramagnetic behavior is observed below T=1 K, providing evidence for the presence of unfrozen spins below Tf (entropic clusters).

Néel to spin-glass-like phase transition versus dilution in geometrically frustratedZnCr2−2xGa2xLee1, Ratcliff2, Huang3 et al. 2008Phys. Rev. B

“…Energy integrated inelastic scattering data over 0.3 meV <hω < 0.6 meV show a broad maximum at around 10 K indicating the critical scattering at the phase transition. Bulk susceptibility data with a maximum at a lower temperature T f = 1.8 K [40] show that this apparent critical temperature is not unique but decreases with the energy scale of the measurement. Such behavior, which is characteristic of spin glasses, indicates that a precipitous softening of the magnetic fluctuation spectrum takes place upon lowing the temperature, leading to anomalies when the lowest energy scale of the system falls below the characteristic energy scale of the measurement.…”

“…Néel temperature TN and spin freezing temperature T f represented by circles are the data obtained by bulk susceptibility measurements reported in Ref. [40]. TN represented by squares and <S> S in the inset are obtained by our neutron scattering measurements, which is discussed in the Sections IV and V.…”

“…13 shows the spatial correlations of the fluctuating moments with different energies. The low energy lying In this section, we study spin correlations in ZnCr 1.4 Ga 0.6 O 4 which exhibits spin-glass-like behaviors in bulk susceptibility measurements [40]. Fig.…”

“…The effect of site disorder on the magnetic correlations and phase transition in ZnCr 2 O 4 by doping nonmagnetic Ga ions into Cr sites has been previously studied by Fiorani et al using bulk property measurements and neutron powder diffractions in the ZnCr 2−2x Ga 2x O 4 series [40]. Fig.…”

High Field ESR of the Frustrated Antiferromagnet Ba2Sn2Ga3ZnCr7O22on a Pyrochlore Slab

“…14,15) Another well studied frustrating system is an insulating spinel ZnCr 2 O 4 . [8][9][10] The magnetic ions on the octahedral B sites of the cubic spinel structure form the pyrochlore lattice so that the spin frustration is expected if the dominant nearest-neighbor interactions are antiferromagnetic. The crystal lattice of ZnCr 2 O 4 deformed from cubic into tetragonal structure at Néel temperature to reduce the spin frustration, as a result, a magnetic order occurs at T N =13.5 K, which is far less than the observed Weiss temperature.…”