Effects of interactions on the relaxation processes in magnetic nanostructures

TY - JOUR

T1 - Effects of interactions on the relaxation processes in magnetic nanostructures

AU - Atkinson, Lewis J.

AU - Ostler, Thomas A.

AU - Hovorka, O.

AU - Wang, K. K.

AU - Lu, B.

AU - Ju, G. P.

AU - Hohlfeld, J.

AU - Bergman, B.

AU - Koopmans, B.

AU - Chantrell, Roy W.

N1 - ©2016 American Physical Society. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.

PY - 2016/10/28

Y1 - 2016/10/28

N2 - Controlling the relaxation of magnetization in magnetic nanostructures is key to optimizing magnetic storage device performance. This relaxation is governed by both intrinsic and extrinsic relaxation mechanisms and with the latter strongly dependent on the interactions between the nanostructures. In the present work we investigate laser induced magnetization dynamics in a broadband optical resonance type experiment revealing the role of interactions between nanostructures on the relaxation processes of granular magnetic structures. The results are corroborated by constructing a temperature dependent numerical micromagnetic model of magnetization dynamics based on the Landau-Lifshitz-Bloch equation. The model predicts a strong dependence of damping on the key material properties of coupled granular nanostructures in good agreement with the experimental data. We show that the intergranular, magnetostatic and exchange interactions provide a large extrinsic contribution to the damping. Finally we show that the mechanism can be attributed to an increase in spin-wave degeneracy with the ferromagnetic resonance mode as revealed by semianalytical spin-wave calculations.

AB - Controlling the relaxation of magnetization in magnetic nanostructures is key to optimizing magnetic storage device performance. This relaxation is governed by both intrinsic and extrinsic relaxation mechanisms and with the latter strongly dependent on the interactions between the nanostructures. In the present work we investigate laser induced magnetization dynamics in a broadband optical resonance type experiment revealing the role of interactions between nanostructures on the relaxation processes of granular magnetic structures. The results are corroborated by constructing a temperature dependent numerical micromagnetic model of magnetization dynamics based on the Landau-Lifshitz-Bloch equation. The model predicts a strong dependence of damping on the key material properties of coupled granular nanostructures in good agreement with the experimental data. We show that the intergranular, magnetostatic and exchange interactions provide a large extrinsic contribution to the damping. Finally we show that the mechanism can be attributed to an increase in spin-wave degeneracy with the ferromagnetic resonance mode as revealed by semianalytical spin-wave calculations.

UR - http://www.scopus.com/inward/record.url?scp=84994275798&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.94.134431

DO - 10.1103/PhysRevB.94.134431

M3 - Article

AN - SCOPUS:84994275798

SN - 1098-0121

VL - 94

SP - 1

EP - 8

JO - Physical Review B

JF - Physical Review B

IS - 13

M1 - 134431

ER -