Influence of Concentration Fluctuations on Relaxation Processes in Spin Glasses

Using the unique combination of atomically resolved atom probe tomography (APT) and volume averaged neutron (resonance) spin echo (NRSE and NSE) experiments, the influence of nano-scaled clusters on the spin relaxation in spin glasses was studied. For this purpose, the phase transition from the paramagnetic phase to the spin glass phase in a Fe-Cr spin glass with a composition of Fe17.8Cr82.2 was studied in detail by means of NRSE. The microstructure was characterised by APT measurements, which show local concentration fluctuations of Fe and Cr on a length scale of 2 to 5 nm, which lead i) to the coexistence of ferro- and anti-ferromagnetic clusters and ii) a change of the magnetic properties of the whole sample, even in the spin glass phase, where spins are supposed to be randomly frozen. We show that a generalized spin glass relaxation function, which was successfully used to describe the phase transition in diluted spin glasses, can also be used for fitting the spin dynamics in spin glasses with significant concentration fluctuations.

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Influence of Concentration Fluctuations on Relaxation Processes in Spin Glasses

Quantum Beam Science ◽

10.3390/qubs2040026 ◽

2018 ◽

Vol 2 (4) ◽

pp. 26 ◽

Cited By ~ 2

Author(s):

Julia Wagner ◽

Wolfgang Häußler ◽

Olaf Holderer ◽

Andreas Bauer ◽

Stephen Shapiro ◽

...

Keyword(s):

Phase Transition ◽

Spin Glass ◽

Spin Glasses ◽

Glass Phase ◽

Concentration Fluctuations ◽

Neutron Resonance ◽

Relaxation Processes ◽

Local Concentration ◽

Spin Glass Phase ◽

Resonance Spin

Using the unique combination of atomically resolved atom probe tomography (APT) and volume averaged neutron (resonance) spin echo (NRSE and NSE) experiments, the influence of nano-scaled clusters on the spin relaxation in spin glasses was studied. For this purpose, the phase transition from the paramagnetic phase to the spin glass phase in an Fe-Cr spin glass with a composition of Fe 17 . 8 Cr 82 . 2 was studied in detail by means of NRSE. The microstructure was characterised by APT measurements, which show local concentration fluctuations of Fe and Cr on a length scale of 2 to 5 nm, which lead (i) to the coexistence of ferro- and anti-ferromagnetic clusters and (ii) a change of the magnetic properties of the whole sample, even in the spin glass phase, where spins are supposed to be randomly frozen. We show that a generalized spin glass relaxation function, which was successfully used to describe the phase transition in diluted spin glasses, can also be used for fitting the spin dynamics in spin glasses with significant concentration fluctuations.

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Spin-glass phase transition and behavior of nonlinear susceptibility in the Sherrington-Kirkpatrick model with random fields

Physical Review B ◽

10.1103/physrevb.93.224206 ◽

2016 ◽

Vol 93 (22) ◽

Cited By ~ 6

Author(s):

C. V. Morais ◽

F. M. Zimmer ◽

M. J. Lazo ◽

S. G. Magalhães ◽

F. D. Nobre

Keyword(s):

Phase Transition ◽

Spin Glass ◽

Random Fields ◽

Glass Phase ◽

Nonlinear Susceptibility ◽

Spin Glass Phase ◽

Kirkpatrick Model ◽

And Behavior

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Effect of the paramagnetic to spin-glass phase transition on the fundamental absorption edge of MnIn2Se4 magnetic semiconducting compound

Revista Mexicana de Física ◽

10.31349/revmexfis.65.14 ◽

2018 ◽

Vol 65 (1) ◽

pp. 14

Author(s):

Carlos Gustavo Rincón

Keyword(s):

Phase Transition ◽

Spin Glass ◽

Glass Phase ◽

Energy Gap ◽

Magnetic Moments ◽

Fundamental Absorption Edge ◽

Theoretical Models ◽

Freezing Temperature ◽

Layered Compound ◽

Spin Glass Phase

The temperature dependence of the indirect and direct fundamental band gaps of the layered compound MnIn2Se4,that crystallizes in a rhombohedral defect structure with space group R -3m (D5/3d), was studied by optical absorption spectra. The data were analyzedin terms of current theoretical models that take into account the contribution of antiferromagnetic exchange interaction between spins to the shift of the energy gap EG with T in the vicinity of the critical paramagnetic to spin-glass phase transition. It was established that short- and long-range effect spin correlations dominate the contribution to this shift in the critical region below about 20 K, near the spin-glass freezing temperature Tf, and noncritical one, between about 70 and 160 K, far from Tf, respectively. An intermediate temperature region, compatible with the behaviour expected for a cluster-glass transition where a gradual freezing of the magnetic moments occurs, was also observed.

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