Spin glass behavior in frustrated quantum spin system CuAl₂O₄with a possible orbital liquid state

Abstract

CuAl2O4 is a normal spinel oxide having quantum spin, S=1/2 for Cu is a Jahn-Teller active ion. Thus, we claim that an orbital liquid state is the most likely ground state in CuAl2O4. Of further interest, it also exhibits a large frustration parameter, f = CW/Tm ~67, one of the largest values reported for spinel oxides. Our observations suggest that CuAl2O4 should be a rare example of a frustrated quantum spin glass with a good candidate for an orbital liquid state.

Dynamic spin fluctuations in the frustrated A -site spinel CuAl2O4

“…( 2) and ( 3), which depicts the dynamic nature of the ground state, there is an additional exponential term necessary to fit the tail of the μSR spectra. Like some of the spin-glasses showing exponential decay with moderate spin fluctuations [39,40], the other term can be related to the glassy phenomena observed in the previous bulk magnetic measurements [8] and our NMR results. Therefore, the ground state of CuAl 2 O 4 is composed of a major (x = 0.7) dynamic phase with the sporadic spin fluctuations and a minor (1 − x = 0.3) phase, rendering its glassy nature.…”

“…Another interesting point is that the magnitude of exchange interactions of the system estimated by its Curie-Weiss temperature (θ CW = −140 K) is quite large. Nonetheless, the ground state shows no long-ranged order down to 0.4 K, but a correlated spin state instead emerge at T * = 2.3 K according to both neutron powder diffraction and heat capacity measurements [8]. The frustration factor (|θ CW |/T * ∼ 60) thus obtained, a standard measure of magnetic frustration, puts CuAl 2 O 4 as one of the most frustrated systems among all the T Al 2 O 4 spinels (T = Mn, Fe, Co, Ni, Cu) [10,11].…”

Theoretical evidence of spin-orbital-entangled Jeff=12 state in the 3d transition metal oxide CuAlKim1, Baidya2, Cho3 et al. 2019Phys. Rev. BSelf Cite170171View full textAdd to dashboardCite

“…a=8.083Å, which is consistent with our earlier results from powder samples. 24 The square of the structural factor of each reflection point in Fig. 1c shows good agreement between the observed and calculated intensities.…”

Spin-orbital-lattice entangled states in cubic d1 double perovskites

“…The absence of the clear-cut JT distortion is most likely explained by either quenching of the JT effect or the presence of the dynamical JT effect. The signs for the latter are seen, for example, in alkali-doped fullerides [28][29][30] and various metal compounds [31][32][33][34]. Since the JT effect can give nontrivial influence on electronic properties, the knowledge of its relevance at local metal sites is indispensable for understanding the nature of these materials.…”