Size and fluctuation effects on the dynamics of linear domain walls in an Ising ferromagnet

Kötzler, J.; Grahl, M.; Sessler, I.; Ferré, J.

doi:10.1103/physrevlett.64.2446

Cited by 19 publications

(5 citation statements)

References 21 publications

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“…A maximum of the FMR linewidth near the Curie temperature has been reported in bulk systems [137,3,80] and for Ni(111)/W(110) films previously [146,151]. This was attributed to the presence of critical fluctuations at the phase transition.…”

Section: Spin Fluctuations At the Curie Temperaturementioning

confidence: 85%

“…The magnetic response near the ferro-to paramagnetic transition in bulk ferromagnets was studied for example by Kötzler and co-workers [137] and theoretically described in the framework of mode-mode coupling theory [80]. It is found in uniaxial ferromagnets that the increase in the relaxation rate at T C can be suppressed by magnetic fields on the order of a few hundred mT.…”

Section: Farlementioning

confidence: 99%

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Ferromagnetic resonance of ultrathin metallic layers

1998

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The contribution that the technique of ferromagnetic resonance (FMR) has made to the understanding of the magnetic behaviour of ultrathin single films is reviewed. Experimental methods to measure FMR in situ in ultrahigh vacuum are presented. The temperature dependence of the magnetization, of the magnetic relaxation rate in the vicinity of the Curie temperature, and of the second-and fourth-order magnetic anisotropy energy (MAE) constants can be measured by FMR in situ for magnetic monolayers. Using the cases of Ni/Cu(001) and Gd/W( 110) as examples, the role of the MAE for the quantitative description of temperature-and thickness-dependent reorientation transitions of the magnetization is discussed. Initial results for the anisotropy of the g-factor which is related to the anisotropy of the orbital moment (and the MAE) are presented.

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Section: Spin Fluctuations At the Curie Temperaturementioning

confidence: 85%

Section: Farlementioning

confidence: 99%

Ferromagnetic resonance of ultrathin metallic layers

1998

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“…The first indirect experimental evidence for the transition from Bloch to linear domain walls was obtained from the optical observations of the temperature dependence of the period of the domain structure in YFeO 3 just below T c [26]. Lately the LWs were observed in the dynamical susceptibility experiments on the low-temperature ferromagnets GdCl 3 [27] and LiTbF 4 [28]. In [29,30] the DW mobility was calculated in the whole temperature range, which exibited a deep minimum at T B .…”

Section: Introductionmentioning

confidence: 99%

Bloch-wall phase transition in the spherical model

Garanin

1996

J. Phys. A: Math. Gen.

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The temperature-induced second-order phase transition from Bloch to linear (Ising-like) domain walls in uniaxial ferromagnets is investigated for the model of D-component classical spin vectors in the limit D → ∞. This exactly soluble model is equivalent to the standard spherical model in the homogeneous case, but deviates from it and is free from unphysical behavior in a general inhomogeneous situation. It is shown that the thermal fluctuations of the transverse magnetization in the wall (the Bloch-wall order parameter) result in the diminishing of the wall transition temperature TB in comparison to its mean-field value, thus favouring the existence of linear walls. For finite values of TB an additional anisotropy in the basis plane x, y is required; in purely uniaxial ferromagnets a domain wall behaves like a 2-dimensional system with a continuous spin symmetry and does not order into the Bloch one. †

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“…x 0 ͑T ͒ diverges at T c 1.53 K, below which the Ho spins order ferromagnetically [14,15]. At the identical temperature, there is a sharp increase in x 00 ͑T ͒, most likely due to the motion of domain walls [16]. We use this feature in x 00 , which occurs at the transition for all transverse fields and temperature studied, as an independent criterion to establish T c (or H c t ).…”

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confidence: 99%

Quantum Critical Behavior for a Model Magnet

Bitko

Rosenbaum

Aeppli³

1996

Phys. Rev. Lett.

270

360

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The classical, thermally driven transition in the dipolar-coupled Ising ferromagnet LiHoF 4 ͑T c 1.53 K͒ can be converted into a quantum transition driven by a transverse magnetic field H t at T 0. The transverse field, applied perpendicular to the Ising axis, introduces channels for quantum relaxation, thereby depressing T c . We have determined the phase diagram in the H t -T plane via magnetic susceptibility measurements. The critical exponent, g 1, has a mean-field value in both the classical and quantum limits. A solution of the full mean-field Hamiltonian using the known LiHoF 4 crystal-field wave functions, including nuclear hyperfine terms, accurately matches experiment. [S0031-9007(96) Quantum phase transitions can differ fundamentally from their classical counterparts because of the unparalleled influence of the dynamics on the T 0 static critical behavior [1]. In addition, unusual electronic and magnetic behavior can arise at nonzero temperature. Thus includes the peculiar mix of the spin and charge degrees of freedom in transition-metal oxides [2], the apparent "non-Fermi-liquid" behavior of highly correlated f-electron compounds [3,4], and the unusual normal-state properties of the high-T c superconducting cuprates [5][6][7][8]. The remarkable properties of these systems have been ascribed in each case to the proximity of a T 0 quantum critical point.There remain considerable experimental and theoretical barriers to describing quantum phase transitions with fidelity and precision. In the high-temperature superconductors, for example, the superconductivity masks the direct study of the quantum order-disorder transition. In heavy-fermion materials, characterization of the T 0 magnetic instability is complicated by the presence of charge carriers and by substitutional disorder. In spin glasses [9], the combination of frustration and disorder impedes consensus on a correct description of even the thermally driven transition. Moreover, despite their power and elegance, pressure-tuning studies of quantum critical points [2,3,10] cannot approach the exactitude which has become the hallmark of experiments on classical critical phenomena.High-precision measurements of quantum critical behavior in clean, insulating magnets simply do not exist, even with the great current interest in quantum phase transitions. Therefore, we have carried out such measurements for a model magnet LiHoF 4 . The key conclusion is that the quantum critical behavior is mean-fieldlike, as predicted by long-standing and elegant theory identifying ͑T 0͒ quantum phase transitions in d dimensions with thermal phase transitions in d 1 1 dimensions [11]. Furthermore, a mean-field theory using known magnetic parameters quantitatively describes the observed magnetic susceptibility in both the quantum and the thermal regimes.LiHoF 4 in an external field H t is the experimental realization of the simplest quantum spin model, namely, the Ising magnet in a transverse magnetic field. The corresponding Hamiltonian iswhere the s's are Pauli spin mat...

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Size and fluctuation effects on the dynamics of linear domain walls in an Ising ferromagnet

Cited by 19 publications

References 21 publications

Ferromagnetic resonance of ultrathin metallic layers

Ferromagnetic resonance of ultrathin metallic layers

Bloch-wall phase transition in the spherical model

Quantum Critical Behavior for a Model Magnet

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