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Wednesday, July 22, 2020 | History

2 edition of Theory of the spin-density-wave phase of MnSi. found in the catalog.

Theory of the spin-density-wave phase of MnSi.

Martin Plumer

Theory of the spin-density-wave phase of MnSi.

by Martin Plumer

  • 131 Want to read
  • 38 Currently reading

Published .
Written in English

    Subjects:
  • Physics Theses

  • Edition Notes

    Thesis (Ph.D.), Dept. of Physics, University of Toronto

    ContributionsWalker, Michael B. (supervisor)
    The Physical Object
    Pagination133 leaves.
    Number of Pages133
    ID Numbers
    Open LibraryOL14734648M

    For MnSi, as the magnetic field increases from 0 T to T, the equilibrium value of in the skyrmion phase decreases from to As a result, the coefficient of the linear term of K changes sign as the magnetic field increases, which is responsible for the configurational reversal of u S 1 and. Spin-density wave (SDW) and charge-density wave (CDW) are names for two similar low-energy ordered states of solids. Both these states occur at low temperature in anisotropic, low-dimensional materials or in metals that have high densities of states at the Fermi level ().Other low-temperature ground states that occur in such materials are superconductivity, ferromagnetism and .

      This prediction was later realized in the A-phase of MnSi and was soon found to be an ubiquitous phase in thin-film chiral ferromagnets. In addition to the standard Ginzburg–Landau analysis, modern approaches to skyrmion crystal phase such as classical Monte Carlo simulation and CP \(^1\) theory are discussed. Muon spin rotation (μ SR) spectra recorded for manganese silicide MnSi and interpreted in terms of a quantitative analysis constrained by symmetry arguments were recently published. The magnetic structures of MnSi in zero-field at low temperature and in the conical phase near the magnetic phase transition were shown to substantially deviate from the expected helical and conical structures.

      MnSi is an itinerant magnet which at low temperatures develops a helical spin-density wave. Under pressure it undergoes a transition into an unusual partially ordered state whose nature is debated. Here we propose that the helical spin crystal (the magnetic analog of a solid) is a useful starting point to understand partial order in MnSi. MnSi [], Fe 1 x Co x Si [4] and FeGe [5, 6] have been attracting continuous attentions due to their interesting physics and potential applications for future memory technology. Specifically, a helical order with a single ordering wave vector k (point along the [] axis in MnSi, for.


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Theory of the spin-density-wave phase of MnSi by Martin Plumer Download PDF EPUB FB2

M L Plumer and M B Walker the theory is that the spin-density-wave polarisation vector S is always perpendicular to Q so that Q and S rotate I it was shown that, for T -G TN0, a second-order phase transition takes place whenHis applied along a () or () by: The theory describes the experimentally observed spin-density-wave wavevector, Q,(')and polarization vector rotation induced by the application of a magnetic field to MnSi and predicts associated second-order phase transitions if the field is along a or symmetry : Martin Louis Plumer.

Request PDF | Magnetoelastic effects in the spin-density wave phase of MnSi | Magnetoelastic interactions are included in a Landau-type free energy, which serves as a basis for the investigation. A spin-density wave must undergo relative phase shifts between its spin-up and spin-down components in order to realize a qualitatively similar type of coupling.

In spite of these limitations, eqn [20] provides a surprisingly good account of the frequency-dependent conductivity observed in most spin-density wave.

A phenomenological model for the magnetostriction near the phase transition marked by field-induced wavevector and spin reorientations fits the observed behaviour well.

Introduction A helical spin-density wave with wavevector Q in a (Ill) direction exists in the cubic metallic compound MnSi below the NCel temperature T, = 29 K. An Cited by: 9.

The transition-metal compound MnSi above a certain pressure (pc = kbar) provides what may be the cleanest example of an extended non-Fermi-liquid phase in.

Magnetoelastic interactions are included in a Landau-type free energy, which serves as a basis for the investigation of strains in the helically polarised spin-density-wave phase of MnSi.

The existence of linearly and helically polarised lattice-displacement waves at Q and 2Q respectively (where Q is the spin-density-wave wavevector) and a.

THE CUBIC intermetallic compound MnSi has been revealed to be an itinerant electron magnet with a helical spin density wave (HSDW) below the Nl temperature TN = 30K,[1, 2]. Many experimental investigations suggest that MnSi is a typical example having various properties of weak ferromagnetism [3].

Theory of helical magnetic structures and phase transitions in MnSi and FeGe Article in Journal of Physics C Solid State Physics 13(31):L November with Reads How we measure 'reads'. Franus-Muir E, Plumer M and Fawcett E Magnetostriction in the spin-density-wave phase of MnSi J.

Phys. C: Solid State Phys. 17 IOPscience Google Scholar [29]. Critical fluctuations in the paramagnetic phase of Cr are considerably more volume dependent than the long range magnetic order, the Grüneisen parameter, Γ + = −, above the Néel temperature T N being about a factor 4 larger than the value, Γ − = −40, below T available thermophysical data for MnSi and Mn 3 Si are analysed to show that in these two spin-density wave.

The long-period helical magnetic structures in MnSi and FeGe are shown to be consequences of a ferromagnetic Dzyaloshinskii instability (). Renormalisation group theory predicts the transition to be first order, in agreement with experiments on MnSi.

A mean-field theory of spin-density-wave wavevector and polarisation vector rotation induced by the application of a magnetic field to MnSi in its spin-density-wave phase, and a prediction of the. Since the late s, MnSi has played a major role in developing the theory of helical magnets in non-centrosymmetric materials showing the Dzyaloshinsky-Moriya interaction (DMI).

With a long helimagnetic pitch of Å as compared to the lattice d-spacing of Å, it was ideal for performing neutron studies, especially as large single crystals could be grown. A (B-T)-phase. The magnetization of MnSi has been measured at low temperatures down to K under high pressures up to P= GPa and magnetic fields up to B=9 T.

MnSi is an itinerant magnet which at low temperatures develops a helical spin-density wave. Under pressure it undergoes a transition into an unusual partially ordered state whose nature is debated.

Here, we quantitatively analyze a high-statistic zero-field muon spin rotation spectrum recorded in the magnetically ordered phase of MnSi by exploiting the result of representation theory as.

Uemura, Y. et al. Phase separation and suppression of critical dynamics at quantum transitions of itinerant magnets: MnSi and (Sr1–x Ca x)RuO3. Nature Phys. 3, 29–35 (). lack of inversion symmetry, in the spin-orbit coupling of MnSi there appears term D(S1 ×S2):Q favoring the perpendicular spin orientation which stabi-lizes the helical spin density wave [11].

MnSi shows a magnetic transition at Tc = K from a paramagnetic state to a helical magnetic structure. The spiral has a wavelength of ˚A in. Among them, MnSi has been studied most extensively and revealed to be a helical magnet whose Néel temperature T N is 29 K [4].

According to the neutron diffraction experiments performed by ISHIKAWA et al., this helical spin density wave (HSDW) has the peculiar properties as follows [4,5]: (i) The period is very long ( Å). () Theory of helical magnetic structures and phase transitions in MnSi and FeGe.

J Phys C: Solid St Phys L  Journal of Magnetism and Magnetic Materials () North-Holland M ~" M M0~ Magnetisation study of the magnetic phase diagram in MnSi C.I. Gregory a, D.B. Lambrick b and N.R. Bernhoeft a Department of Physics, University of Durham, Durham, UK b Department of Physics and Mathematics, Manchester Polytechnic, Manchester, UK Magnetisation measurements .derived by group theory.

Within the model, we establish the methodology to calculate the phase diagram and equilibrium properties of helimagnets under coupled temperature-magneto-elastic field. Applying the model to bulk MnSi, we calculate the temperature-magnetic field phase diagram under.