Nonlinear Susceptibility of Ni near the Curie Temperature

Shirane, Takashi; Moriya, T.; Bitoh, Teruo; Sawada, Akira; Aida, Hiroyuki; Chikazawa, Susumu

doi:10.1143/jpsj.64.951

Cited by 21 publications

(20 citation statements)

References 22 publications

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“…The in-phase nonlinear susceptibility shows a dip at 80 K with decreasing temperature and peaks at around 60 K, being compatible with the description of ferromagnetic phase transition, where the nonlinear susceptibility diverges negatively and positively on both sides of the ferromagnetic transition temperature [5]. Also, a negative peak is clearly seen in the out-of-phase nonlinear susceptibility, characteristic of ferromagnetic transition [6].It should also be noted that smaller particles show a larger susceptibility at low temperatures (not shown), indicating that the surface region of the LaCoO 3 particle is likely ferromagnetic. These results are in agreement with our previous observation on the ferromagnetic domain patterns of a LaCoO 3 single crystal and particles [2].…”

supporting

confidence: 82%

supporting

confidence: 82%

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Surface ferromagnetism of LaCoO3 crystals

Harada

Taniyama

Itoh

2007

Journal of Magnetism and Magnetic Materials

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supporting

confidence: 82%

supporting

confidence: 82%

Surface ferromagnetism of LaCoO3 crystals

Harada

Taniyama

Itoh

2007

Journal of Magnetism and Magnetic Materials

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“…However, χ 0 (ω) ′ in Fig. 1(b) does not dip but peaks at ∼ 37 K and ∼ 60 K, indicating that the nonlinear component is becoming significant at the peak temperature (T p ) as in ferromagnets, spin-glass and cluster-glass materials [18,19]. In addition, the nonlinear susceptibilities χ ′ 2 and χ ′′ 2 peak at the same temperature.…”

mentioning

confidence: 92%

Mixed Magnetic Phases in(Ga,Mn)AsEpilayers

et al. 2005

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Two different ferromagnetic-paramagnetic transitions are detected in (Ga,Mn)As/GaAs(001) epilayers from ac susceptibility measurements: transition at a higher temperature results from (Ga,Mn)As cluster phases with [110] uniaxial anisotropy and that at a lower temperature is associated with a ferromagnetic (Ga,Mn)As matrix with 100 cubic anisotropy. A change in the magnetic easy axis from [100] to [110] with increasing temperature can be explained by the reduced contribution of 100 cubic anisotropy to the magnetic properties above the transition temperature of the (Ga,Mn)As matrix.Ferromagnetism in Mn-doped p−type semiconductors can theoretically be understood by the p − d exchange interaction between hole carriers and doped Mn spins [1,2,3,4], which can be manipulated by electric-field [5] or optical-hole generation [6]. Recent studies of magnetic anisotropy in (Ga,Mn)As/GaAs(001) epilayers, on the other hand, have shown a significant change in the magnetic anisotropy with increasing temperature [7,8,9,10]; uniaxial anisotropy along [110] ([110] uniaxial anisotropy) [7,8,9,10,11,12] becomes predominant with increasing temperature [7,8,9, 10] as well as increasing hole concentration [13]. In spite of these intensive studies, the origin of [110] uniaxial anisotropy is still unclear within the current theoretical framework and an understanding of the change in the magnetic anisotropy with temperature is therefore of fundamental importance in revealing the physics of magnetic semiconductors.The aim of this study is to give a comprehensive description of the magnetic anisotropy in (Ga,Mn)As epilayers.In this Letter, two different peaks in temperature-dependent ac susceptibility that are associated with ferromagnetic-paramagnetic transitions are clearly shown. The peak profile at a higher transition temperature has a considerable dependence on frequency, indicating a blocking process in magnetic clusters, while that at a lower transition temperature shows no frequency dependence. The results provide evidence that the magnetic transitions at the lower and higher temperatures are associated with magnetic phases with cubic anisotropy and [110] uniaxial anisotropies, respectively, and the crossover of the magnetic easy axis from 100 to [110] can be interpreted by the ferromagneticparamagnetic transition of the magnetic phase with 100 cubic magnetocrystalline anisotropy accordingly. 100 nm-thick (Ga,Mn)As epilayers were grown on top of a 400-nm-thick GaAs buffer layer grown at 590• C on a semi-insulating GaAs (001) substrate using lowtemperature molecular beam epitaxy (MBE) at 190 − 235• C under an As-rich growth condition. To increase the hole carrier concentration, some epilayers were subject to post-growth annealing in an N 2 atmosphere for 60 − 240 min at 250• C [14]; hole concentration was controlled by changing the Mn content and/or lowtemperature annealing [13]. Hole carrier concentrations p (= ionized Mn acceptor concentration) were measured with electrochemical capacitance-voltage (ECV) method at room temper...

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“…Apart from this, the theoretical understanding about the non-linear susceptibilities is far from being satisfactory as far as these magnetic systems are concerned, though treatments of the critical regimes based on the simple mean field models [30] as well as more complicated Sherrington-Kirkpatric [31], Bethe approximation models [32] exist. However, there are a few experimental studies of the third ordered susceptibility (χ 3 ) on ferromagnetic systems [30,33,34] which though predominantly qualitative in nature have included attempts on characterizing these transitions by the determination of the critical exponents. Recently, a study has been made to understand the hysteresis effect in ferromagnet through the measurement of non-linear susceptibilities [35].…”

Section: Probing Long Range Orderingmentioning

confidence: 99%