Magnetization reversal of micropattern Fe bar array: Combination of vector and Bragg magneto-optical Kerr effect measurements

Westphalen, A.; Theis‐Bröhl, Katharina; Zabel, H.; Rott, Karsten; Brückl, Hubert

doi:10.1016/j.jmmm.2005.09.005

Cited by 17 publications

(14 citation statements)

References 15 publications

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“…There are a number of papers in this field tackling the problems of magneto-optics [6][7][8], opto-acoustics [9,10], and plasmonics [11][12][13], often extending the experimental approaches into the nonlinear domain [14] or employing time-resolved techniques [15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Femtosecond laser-induced optical anisotropy in a two-dimensional lattice of magnetic dots

et al. 2014

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Using pump-probe optical polarimetry we demonstrate that femtosecond laser excitation of a 2D regular lattice of magnetic nanodots effectively changes the optical anisotropy of the array. Study of the dynamics of the femtosecond laser-induced anisotropy reveals four main mechanisms occurring in the electronic, spin, and lattice subsystems. Below 1 ps, a strong Kerr-like nonlinearity causes linear birefringence, with its axis directed along the electric field of the linearly polarized femtosecond laser pump pulse. In addition, a long-living linear birefringence is also induced due to slowly relaxing excitations. Also below 1 ps, ultrafast laser-induced demagnetization of Co leads to a partial breakdown of the circular birefringence of the magnetic nanodots. On the timescale up to 300 ps, optically triggered acoustic modes of the dots drive oscillations of the linear optical birefringence. During this process, the oscillations damp while transferring their energy into acoustic modes of the substrate. On the nanosecond timescale, the signal is dominated by acoustic oscillations at the surface of the substrate.

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Section: Introductionmentioning

confidence: 99%

Femtosecond laser-induced optical anisotropy in a two-dimensional lattice of magnetic dots

et al. 2014

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“…The initial EB direction is set by an annealing step after deposition for 1 h at 548 K which is higher then the blocking temperature[3] of exchange bias systems having IrMn layer as the AF layer. The annealing magnetic field H ann = 1 kOe was applied and maintained parallel to the film plane [26].The sample was measured using a vector-MOKE setup [27]. A number of 360 pairs of L-and T-components of the magnetization (m || and m ⊥ respectively)…”

mentioning

confidence: 99%

Quantitative description of the azimuthal dependence of the exchange bias effect

Radu¹,

Westphalen²,

Theis‐Bröhl³

et al. 2005

J. Phys.: Condens. Matter

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While the principal features of the exchange bias between a ferromagnet and an antiferromagnet are believed to be understood, a quantitative description is still lacking. We show that interface spin disorder is the main reason for the discrepancy of model calculations versus experimental results. Taking into account spin disorder at the interface between the ferromagnet and the antiferromagnet by modifying the well known Meiklejohn and Bean model, an almost perfect agreement can be reached. As an example this is demonstrated for the CoFe/IrMn exchange biased bilayer by analyzing the azimuthal dependence of magnetic hysteresis loops from MOKE measurements. Both, exchange bias and coercive fields for the complete 360• angular range are reproduced by our model. The exchange bias system refers to the shift of the ferromagnetic (F) hysteresis loop to positive or negative values when the F system is in contact with an antiferromagnetic (AF) system and cooled in an applied magnetic field through the Néel temperature of the AF system. The exchange bias (EB) phenomenon is associated with the interfacial exchange coupling between ferromagnetic and antiferromagnetic spin structures, resulting in a unidirectional magnetic anisotropy [1]. While the unidirectional anisotropy was successfully introduced by Meiklejohn and Bean (M&B), the origin of the enhanced coercive field is yet not well understood. The details of the EB effect depend crucially on the AF/F combination chosen and on the structure and thickness of the films [2,3]. However, some characteristic features apply to most systems: (1) H EB and H c increase as the system is cooled in an applied magnetic field below the blocking temperature T B ≤ T N of the AF layer, where T N is the Néel temperature of the AF layer; (2) the magnetization reversal can be different for the ascending and descending part of the hysteresis loop [4,5,6,7,8]; (3) thermal relaxation effects of H EB and H c indicate that a stable magnetic state is reached only at very low temperatures [9,10,11].Several theoretical models have been developed for describing possible mechanisms of the EB effect, including domain formation in the AF layer with domain walls perpendicular to the AF/F interface [12], creation of uncompensated excess AF spins at the interface [13], or the formation of domain walls in the AF layer parallel to the interface [14,15]. Another approach is the consideration of diluted antiferromagnets in an exchange field. In the work described in Ref. [16,17,18] the discussion about compensated versus uncompensated interfacial spins is replaced by a discussion of net magnetic moments within the antiferromagnetic layer. Depending on the complexity of the system, the models can explain some but not * florin.radu@bessy.de † Present address: BESSY GmbH, Albert-Einstein-Str. 15, D-12489 Berlin, Germany.all features of experimental hysteresis loops. Here we provide a new model which can describe all features, including the azimuthal dependence of H EB , H c , and the AF thickness dependence. In ...

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“…Similar to optical and X-ray diffraction, the n th order diffraction spot represents the n th order Fourier transform of the structural form factor. We have recently extended the Bragg MOKE method such that vector MOKE [26,33] can be combined with Bragg MOKE [27], which allows to determine the complete magnetization vector in the sample plane at a specific diffraction spot [8]. This has the additional advantage that only the periodic part of the MOKE signal is filtered out from all other effects which may contribute to the total MOKE signal.…”

Section: Moke Setupmentioning

confidence: 99%

Magnetization reversal of microsized Fe elliptic rings

Westphalen

Remhof

Zabel

2010

Journal of Magnetism and Magnetic Materials

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Magnetization reversal of micropattern Fe bar array: Combination of vector and Bragg magneto-optical Kerr effect measurements

Cited by 17 publications

References 15 publications

Femtosecond laser-induced optical anisotropy in a two-dimensional lattice of magnetic dots

Femtosecond laser-induced optical anisotropy in a two-dimensional lattice of magnetic dots

Quantitative description of the azimuthal dependence of the exchange bias effect

Magnetization reversal of microsized Fe elliptic rings

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