Spontaneous magnetization of quantum XY spin model in joint presence of quenched and annealed disorder

Abstract

We investigate equilibrium statistical properties of the quantum XY spin-1/2 model in an external magnetic field when the interaction and field parts are subjected to quenched or/and annealed disorder. The randomness present in the system are termed annealed or quenched depending on the relation between two different time scales -the time scale associated with the equilibriation of the randomness and the time of observation. Within a mean-field framework, we study the effects of disorders on spontaneous magnetization, both by perturbative and numerical techniques. Our primary interest is to understand the differences between quenched and annealed cases, and also to investigate the interplay when both of them are present in a system. We observe in particular that when interaction and field terms are respectively quenched and annealed, critical temperature for the system to magnetize in the direction parallel to the applied field does not depend on any of the disorders. Further, an annealed disordered interaction neither affects the magnetizations nor the critical temperatures. We carry out a comparative study of the different combinations of the disorders in the interaction and field terms, and point out their generic features.

Strong anisotropy in the mixed antiferromagnetic system Mn1−xFexPSe3

“…For low-dimensional systems, the value of T N as measured by specific heat is not always directly correlated to the maximum in the susceptibility versus T , and a broad maximum above T N is caused by short-range spin correlations. [14][15][16][17] Here the T N from heat capacity ( Figure 5) is more closely tracked by the point where the slope of the χ − T curve is maximized. The heat capacity of the x = 0.5 sample shows no lambda anomaly, although the general features of the susceptibility vary smoothly with x. Curie-Weiss temperatures θ and effective magnetic moments (µ eff ) were extracted from the susceptibility over the 280-400 K temperature range.…”

“…This peak broadens further into a diffuse, but still detectable, contribution at 150 K, which is higher than T N = 124 K for FePSe 3 , indicating short-range magnetic correlations that are common for low-dimensional materials. [15][16][17] For a higher-angle11 21 2 magnetic peak, the correlation lengths are not determinable within the limits of instrumental and sample broadening.…”

Pseudospin exchange interactions ind7cobalt compounds: Possible realization of the Kitaev model

“…Recently, new cobalt compounds Na 2 Co 2 TeO 6 and Na 3 Co 2 SbO 6 with a nearly perfect honeycomb lattice of magnetic Co 2+ d 7 ions have been synthesized and studied [23][24][25][26]. Both these two systems develop a zigzagtype antiferromagnetic order at low temperatures, analogous to that observed in d 5 pseudospin-1/2 materials RuCl 3 and Na 2 IrO 3 .…”

“…Our study is partially motivated by the recent experiments [23][24][25][26] on cobalt compounds Na 2 Co 2 TeO 6 and Na 3 Co 2 SbO 6 with a layered hexagonal structure. In both systems, the d 7 ions Co 2+ form a nearly perfect honeycomb lattice and develop a zigzag-type antiferromagnetic order at low temperatures, analogous to that observed in d 5 pseudospin-1/2 materials RuCl 3 and Na 2 IrO 3 .…”

Person-Situation Debate Revisited: Phase Transitions with Quenched and Annealed Disorders

“…Disorders may also modify the character or the strength of interactions [22,23]. Regardless of their origin and nature, we can distinguish two types of disturbances based on the time-scale of their appearance [23][24][25]. Disorder is said to be quenched when it does not evolve in time.…”