Magnetic properties of the premartensitic transition in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ni</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mi mathvariant="normal">MnGa</mml:mi></mml:math>alloys

Zuo, F.; Su, Xiaoqiang; Wu, Kuang‐Hsi

doi:10.1103/physrevb.58.11127

Cited by 80 publications

(62 citation statements)

References 11 publications

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“…Should an increase in the frequencies of the soft phonons exist, it would be consistent with macroscopic measurements that report a decrease of the intermediate transition temperature with increasing magnetic field. 10,23 …”

Section: Resultsmentioning

confidence: 99%

Phonon softening inNi−Mn−Gaalloys

et al. 2001

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The TA 2 phonon dispersion curves of Ni-Mn-Ga alloys with different compositions which transform to different martensitic structures have been measured over a broad temperature range covering both paramagnetic and ferromagnetic phases. The branches show an anomaly ͑dip͒ at a wave number that depends on the particular martensitic structure, and there is softening of these anomalous phonons with decreasing temperature. This softening is enhanced below the Curie point, as a consequence of spin-phonon coupling. This effect is stronger for systems with higher electronic concentration.

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Section: Resultsmentioning

confidence: 99%

Phonon softening inNi−Mn−Gaalloys

et al. 2001

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“…Figure 18a shows a phase diagram of Ni 2+x Mn 1−x Ga alloys built numerically with allowance for Eqn (29). The following values of the parameters in Eqns (12) and (29) (see Refs [14,20,21,23,66,67,80,91,123,223]) were …”

Section: T Vs X Phase Diagram At Tm ≈ Tcmentioning

confidence: 99%

“…The resulting system of nonlinear algebraic equations can be solved only numerically. To do the necessary numerical calculations, the following values of parameters in equation (12) were chosen on the basis of the existing experimental data [14,20,21,23,66,67,80,91,123,223] The other parameters were taken from Eqn (30). The experimental data (see Fig.…”

Section: T Vs X Phase Diagram At Tm ≈ Tcmentioning

confidence: 99%

Shape memory ferromagnets

Васильев¹,

Buchelnikov²,

Takagi³

et al. 2003

Phys.-Usp.

249

135

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In ferromagnetic alloys with shape memory large reversible strains can be obtained by rearranging the martensitic domain structure by a magnetic field. Magnetization through displacement of domain walls is possible in the presence of high magnetocrystalline anisotropy, when martensitic structure rearrangement is energetically favorable compared to the reorientation of magnetic moments. In ferromagnetic Heusler alloys Ni2+xMn1−xGa the Curie temperature exceeds the martensitic transformation temperature. The fact that these two temperatures are close to room temperature offers the possibility of magnetically controlling the shape and size of ferromagnets in the martensitic state. In Ni2+xMn1−xGa single crystals, a reversible strain of ∼ 6% is obtained in fields of ∼ 1 T.

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“…For some samples [9, 11,12] there exists evidence for a true phase transition at Tj of very weak first-order which is driven by a magnetoelastic coupling. The main proof of that is the fact that 7/ shifts with the external applied field [9] while no (significant) magnetic field dependence has been found for the TM temperature [13,15]. Moreover, the magnetoelastic effects have been confirmed from the experimentally observed dependence of the elastic constants on an external magnetic field [16].…”

Section: Introductionmentioning

confidence: 59%

Mean field and Monte Carlo simulation studies of premartensitic effects in Ni₂MnGa

2001

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We have extended the degenerate BEG model [l] to include magnetic degrees of freedom in order to study the premartensitic effects in Ni 2 MnGa. The model is solved by using mean-field theory and Monte Carlo techniques [2]. The numerical simulations reveal the crucial importance of fluctuations in pretransitional effects. Moreover, we find that a large variety of premartensitic effects may appear due to the magnetoelastic coupling. For large values of the coupling parameter a first-order transition line ending in a critical point appears. This critical point is responsible for the existence of large premartensitic fluctuations which manifest as broad peaks in the specific heat, not always associated with a true phase transition. The main conclusion is that premartensitic effects result from the interplay between the softness of the anomalous phonon driving the modulation and the magnetoelastic coupling strength. In particular, the premartensitic transition occurs when such coupling is strong enough to prevent a complete softening of the involved phonon mode. The implication of the results in relation to the available experimental data is discussed.

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Magnetic properties of the premartensitic transition inNi2MnGaalloys

Cited by 80 publications

References 11 publications

Phonon softening inNi−Mn−Gaalloys

Phonon softening inNi−Mn−Gaalloys

Shape memory ferromagnets

Mean field and Monte Carlo simulation studies of premartensitic effects in Ni₂MnGa

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Magnetic properties of the premartensitic transition inNi2MnGaalloys

Cited by 80 publications

References 11 publications

Phonon softening inNi−Mn−Gaalloys

Phonon softening inNi−Mn−Gaalloys

Shape memory ferromagnets

Mean field and Monte Carlo simulation studies of premartensitic effects in Ni2MnGa

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Product

Resources

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Mean field and Monte Carlo simulation studies of premartensitic effects in Ni₂MnGa