Ordered vs. disordered states of the random-field model in three dimensions

Garanin, D. A.; Chudnovsky, Eugene M.

doi:10.1140/epjb/e2015-50604-x

Cited by 12 publications

(7 citation statements)

References 57 publications

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“…If the effects of exchange interaction across the F/AF interface can be described by an effective random field exerted on AF, then its reciprocal effects on F can be similarly described by an effective random field. Indeed, the Heisenberg exchange interaction preserves rotational symmetry, and therefore the local exchange torques exerted across F/AF interface on AF should be opposite to the local torques exerted by AF on F. Theoretical studies have shown that random fields acting on Fs produce an inhomogeneous magnetization state, with the magnitude of deviations from the saturated state related to the external field by certain scaling exponents dependent on the system dimensionality [32][33][34] .…”

Section: Introductionmentioning

confidence: 99%

Experimental demonstration and analysis of random field effects in ferromagnet/antiferromagnet bilayers

2020

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More than 30 years ago, Malozemoff (Phys. Rev. B 35, 3679 (1987)) hypothesized that exchange interaction at the interface between a ferromagnet (F) and an antiferromagnet (AF) can act as an effective random field, which can profoundly affect the magnetic properties of the system. However, until now this hypothesis has not been directly experimentally tested. We utilize magnetoelectronic measurements to analyze the effective exchange fields at Permalloy/CoO interface. Our results cannot be explained in terms of quasi-uniform effective exchange fields, but are in agreement with the random-field hypothesis of Malozemoff. The presented approach opens a new route for the quantitative analysis of effective exchange fields and anisotropies in magnetic heterostructures for memory, sensing and computing applications.

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Section: Introductionmentioning

confidence: 99%

Experimental demonstration and analysis of random field effects in ferromagnet/antiferromagnet bilayers

2020

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“…Another criticism of the IM concept came from its neglect of metastable states [22][23][24] . It was found numerically that the RA magnets exhibited metastability and history dependence 25,26 , although they do break into IM domains of size predicted by theory if one begins with a fully disordered initial state. It was demonstrated that the relation between the number of spin components and dimensionality of space in the random-field model determines whether the model possesses topological defects, and that the latter is crucial for preservation or decay of the long-range correlations [27][28][29] .…”

Section: Introductionmentioning

confidence: 90%

Random Anisotropy Magnet at Finite Temperature

Garanin,

Chudnovsky

2021

Preprint

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We present finite-temperature Monte Carlo studies of a 2D random-anisotropy magnet on lattices containing one million spins. The correlated spin-glass state predicted by analytical theories is reproduced in simulations, as are the field-cooled and zero-field-cooled magnetization curves observed in experiments. The orientations of lattice spins begin to freeze when temperature is lowered. The freezing transition is due to the energy barriers generated by the random anisotropy rather than due to random interactions in conventional spin-glasses. We describe freezing by introducing the time-dependent spin-glass order parameter q and the spin-melting time τM defined via q = τM /t above freezing, where t is the time of the experiment represented by the number of Monte Carlo steps.

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“…The validity of this argument that ignores metastable states, was later questioned by numerical studies [6][7][8] . It was found that the RA magnets exhibit metastability and history dependence 32,33 regardless of the strength of the RA, although the IM argument roughly holds for the average size of ferromagnetically correlated region if one begins with a fully disordered state. More recently, using random-field model, it was demonstrated that the presence of topological defects determined by the relation between the number of spin components and dimensionality of space, is responsible for the properties of random magnets [9][10][11] .…”

Section: Introductionmentioning

confidence: 98%

Nonlinear and Thermal Effects in the Absorption of Microwaves by Random Magnets

Garanin,

Chudnovsky

2021

Preprint

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We study the temperature dependence of the absorption of microwaves by random-anisotropy magnets. It is governed by strong metastability due to the broad distribution of energy barriers separating different spin configurations. At a low microwave power, when the heating is negligible, the spin dynamics is close to linear. It corresponds to the precession of ferromagnetically ordered regions that are in resonance with the microwave field. Previously we have shown (http://doi.org/10.1103/PhysRevB.103.214414) that in this regime a dielectric substance packed with random magnets would be a strong microwave absorber in a broad frequency range. Here we demonstrate that on increasing the power, heating and over barrier spin transitions come into play, resulting in the nonlinear behavior. At elevated temperatures the absorption of microwave power decreases dramatically, making the dielectric substance with random magnets transparent for the microwaves.

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Ordered vs. disordered states of the random-field model in three dimensions

Cited by 12 publications

References 57 publications

Experimental demonstration and analysis of random field effects in ferromagnet/antiferromagnet bilayers

Experimental demonstration and analysis of random field effects in ferromagnet/antiferromagnet bilayers

Random Anisotropy Magnet at Finite Temperature

Nonlinear and Thermal Effects in the Absorption of Microwaves by Random Magnets

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