Specific Heat of the Dilute, Dipolar-Coupled, Ising Magnet LiHoxY1-xF4

Physics & Astronomy;Magnetism;Spin Glass;Low Temperature Physics;Condensed Matter Physics;Disordered Materials;Specific Heat

Quilliam, Jeffrey

University of Waterloo

关键词: Physics & Astronomy;    Magnetism;    Spin Glass;    Low Temperature Physics;    Condensed Matter Physics;    Disordered Materials;    Specific Heat;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/2964/1/jaquilli2006.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

The system LiHo_xY_1-xF₄ is a nearly perfect example of a dilute, dipolar-coupled Isingmagnet and, as such, it is an ideal testing ground for many theories in statistical mechanics.At low holmium concentration (x = 0.045) an unusual spin liquid or ;;anti-glass;; state wasdiscovered in previous work [1]. This state does not exhibit a spin glass freezing transitionas is expected for a long-range interaction. Instead, it shows dynamics which are consistentwith a collection of low-frequency oscillators [2]. It was also seen to have sharp features inits specific heat [3].

We present heat capacity measurements on three samples at and around the concentration of the spin liquid state in zero magnetic field and in a temperature range from around 50 mK to 1 K. In contrast to previous measurements, we find no sharp features in the specific heat. The specific heat is a broad feature which is qualitatively consistent with that of a spin glass. The residual entropy as a function of x, obtained through anumerical integral of the data, however, is consistent with numerical simulations whichpredict a disappearance of spin glass ordering below a critical concentration of dipoles [4].

Also presented here, is ac susceptibility data on an x = 0.45 sample which exhibits aparamagnetic to ferromagnetic transition and is found to be consistent with previous work.