Probabilistic Aspects of Magnetization Relaxation in Single-Domain Nanomagnets

Bertotti, G.; Serpico, C.; Mayergoyz, I.D.

doi:10.1103/physrevlett.110.147205

Cited by 17 publications

(4 citation statements)

References 29 publications

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“…Therefore, there will exist two basins of attraction for the field-induced relaxation. These basins exhibit some degree of interlacing, similarly to what one observes in conventional magnetization relaxation due to intrinsic damping [19], the smaller the field h a , the finer the interlacing. An example, obtained by numerical integration of Eq.…”

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confidence: 64%

Conservative effects in spin-transfer-driven magnetization dynamics

2014

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It is shown that under appropriate conditions spin-transfer-driven magnetization dynamics in a single-domain nanomagnet is conservative in nature and admits a specific integral of motion, which is reduced to the usual magnetic energy when the spin current goes to zero. The existence of this conservation law is connected to the symmetry properties of the dynamics under simultaneous inversion of magnetisation and time. When one applies an external magnetic field parallel to the spin polarization, the dynamics is transformed from conservative into dissipative. More precisely, it is demonstrated that there exists a state function such that the field induces a monotone relaxation of this function toward its minima or maxima, depending on the field orientation. These results hold in the absence of intrinsic damping effects. When intrinsic damping is included in the description, a competition arises between field-induced and damping-induced relaxations, which leads to the appearance of limit cycles, that is, of magnetization self-oscillations.The spin-transfer phenomenon and related spintronic applications have been the focus of considerable research in the past two decades [1][2][3][4][5]. This research has been dominated by experimental and theoretical studies of spin-transfer-induced magnetization switching [6][7][8][9], as well as spin-transfer-driven magnetization selfoscillations [10][11][12][13][14]. These studies have all been based on the seed idea that spin transfer manifests itself as a non-conservative torque that competes with intrinsic (thermal) damping. In particular, it has been realized that the mutual compensation of non-conservative effects caused by spin transfer and thermal damping is the physical mechanism for the formation of magnetization selfoscillations [1,13,15].It is demonstrated in this Letter that in single-domain nanomagnets spin transfer may act as a purely conservative torque when electron spin polarization is directed along the intermediate (i. e., hard in-plane) anisotropy axis. Under these conditions, the following new physical features emerge: the appearance of purely conservative magnetization dynamics with closed precessiontype trajectories; the existence of a special integral of motion for this conservative dynamics, which is reduced to the conventional magnetic energy at zero spin current; a very unique global bifurcation in magnetization dynamics occurring at a specific critical value of the injected spin-polarized current; the conversion of the conservative dynamics into monotone relaxation when an inplane dc magnetic field is applied along the intermediate anisotropy axis; the existence of a Lyapunov function governing these field-induced relaxations as well as the appearance of field-induced interlacing of the basins of attractions of the critical points of the dynamics. The origin of all these new physical features can be traced back to the special symmetry of magnetization dynamics appearing in the case when both electron spin polarization and applied dc magnetic field are...

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confidence: 64%

Conservative effects in spin-transfer-driven magnetization dynamics

2014

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“…The quantities of interest are not always the fast dynamics but the slower ones resulting from thermally driven jumps over energy barriers. Therefore, an alternative approach is to describe the effect of thermal fluctuations as a jump noise process [22][23][24][25], where, based on the energy land scape for each finite difference cell, the switching time and final magnetization direction are determined stochastically and only the resulting changes in the magnetization, instead of all random thermal fluctuations, are considered.…”

Section: Zeeman Energymentioning

confidence: 99%

Fast micromagnetic simulations on GPU—recent advances made with $\mathsf{mumax}^3$

Leliaert

Dvornik

Mulkers

et al. 2018

J. Phys. D: Appl. Phys.

143

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In the last twenty years, numerical modeling has become an indispensable part of magnetism research. It has become a standard tool for both the exploration of new systems and for the interpretation of experimental data. In the last five years, the capabilities of micromagnetic modeling have dramatically increased due to the deployment of graphical processing units (GPU), which have sped up calculations to a factor of 200. This has enabled many studies which were previously unfeasible. In this topical review, we give an overview of this modeling approach and show how it has contributed to the forefront of current magnetism research.

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“…This classical approach proved very efficient and successful in many studies (see e.g. [33][34][35][36][37][38][39][40][41][42][43] and references therein). However, when the size of the magnetic object decreases down to atomic scale, one can wonder about the occurrence of quantal effects.…”

Section: Introductionmentioning

confidence: 99%