Critical phenomena in dipolar magnets

Kötzler, J.

doi:10.1016/0304-8853(86)90197-6

Cited by 28 publications

(5 citation statements)

References 48 publications

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“…These effects are evident in the polarization fluctuations of paranematic RM734, as shown in SI Appendix , Fig. S12 , which also points out the additional important Aharony findings that the resulting anisotropy also makes the transition mean-field-like, rather than fluctuation-dominated with 3D Ising universality, and that the growth of correlation in y is the principal soft mode of the transition ( 72 – 74 ). The corresponding Landau mean field free energy description of the transition can be derived from the Ising/dipolar Hamiltonian ( 55 , 75 ), and applying it to the SmZ A phase results in the F IS model of Eq.…”

Section: Discussion: Modeling the N–smz A –N ...mentioning

confidence: 62%

The smectic Z _A phase: Antiferroelectric smectic order as a prelude to the ferroelectric nematic

Chen

Martinez

Körblová

et al. 2023

Proc. Natl. Acad. Sci. U.S.A.

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We have structurally characterized the liquid crystal (LC) phase that can appear as an intermediate state when a dielectric nematic, having polar disorder of its molecular dipoles, transitions to the almost perfectly polar-ordered ferroelectric nematic. This intermediate phase, which fills a 100-y-old void in the taxonomy of smectic LCs and which we term the “smectic Z A ,” is antiferroelectric, with the nematic director and polarization oriented parallel to smectic layer planes, and the polarization alternating in sign from layer to layer with a 180 Å period. A Landau free energy, originally derived from the Ising model of ferromagnetic ordering of spins in the presence of dipole–dipole interactions, and applied to model incommensurate antiferroelectricity in crystals, describes the key features of the nematic–SmZ A –ferroelectric nematic phase sequence.

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Section: Discussion: Modeling the N–smz A –N ...mentioning

confidence: 62%

The smectic Z _A phase: Antiferroelectric smectic order as a prelude to the ferroelectric nematic

Chen

Martinez

Körblová

et al. 2023

Proc. Natl. Acad. Sci. U.S.A.

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“…5 (b) -(f)) and from Frey and Schwabl 36 using a constant dipolar wavenumber q D = 0.033 Å−1 as reported in Ref. 26 . The experimental and theoretical scaling functions f T exhibit a similar dependence on x, i.e.…”

Section: B Quasielastic Measurementsmentioning

confidence: 99%

“…The thus obtained temperature dependence of the dipolar wave numbers q D is shown in (c), where the blue dashed line reflects the literature value q D = 0.033Å −1 from Ref. 26 . For T C ≤ T ≤ T C + 8 K q D is slightly smaller, while above T C + 8 K, q D is significantly larger than the literature value.…”

Section: B Quasielastic Measurementsmentioning

confidence: 99%

Dipolar effects on the critical fluctuations in Fe: Investigation by the neutron spin-echo technique MIEZE

2017

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Iron is one of the archetypical ferromagnets to study the critical fluctuations at a continuous phase transition thus serving as a model system for the application of scaling theory. We report a comprehensive study of the critical dynamics at the transition from the ferro-to the paramagnetic phase in Fe, employing the high-resolution neutron spin echo technique MIEZE. The results show that the dipolar interactions lead to an additional damping of the critical spin fluctuations at small momentum transfers q. The results agree essentially with scaling theory if the dipolar interactions are taken into account by means of the mode-coupling equations. However, in contrast to expectations, the dipolar wavenumber qD that plays a central role in the scaling function f (κ/q, qD/κ) becomes temperature dependent. In the limit of small q the critical exponent z crosses over from 2.5 to 2.0.

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“…This effect is expected to be strong since the measurements probe the fluctuation modes in the zone centre where the long-range nature of the dipolar interaction dominates the dynamics. This interaction introduces non-conserving terms in the Hamiltonian which prevents the slowing down of the longitudinal (to the wave vector) modes near the Curie temperature, T C (Kötzler 1986). Therefore, if the measured relaxation rate reflects only these modes, it should saturate as the temperature approaches T C .…”

Section: Critical and Low-temperature Spin Dynamics In Ferromagnetsmentioning

confidence: 99%

Muon spin rotation and relaxation in magnetic materials

Réotier¹,

Yaouanc²

1997

J. Phys.: Condens. Matter

197

123

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A review of the muon spin rotation and relaxation (µSR) studies on magnetic materials published from July 1993 is presented. It covers the investigation of magnetic phase diagrams, that of spin dynamics and the analysis of the magnetic properties of superconductors. We have chosen to focus on selected experimental works in these different topics. In addition, a list of published works is provided. Contents1. Introduction 2. µSR: muon spin rotation, relaxation 2.1. The transverse depolarization function 2.2. The longitudinal depolarization function 2.3. The magnetic field at the muon site 3. Magnetic phase diagrams 3.1. Magnetic ordering in organic compounds 3.2. Magnetic ordering in spin chains and ladders 3.3. Diamagnetic domains in beryllium 3.4. Localized and itinerant f electrons in heavy-fermion materials 4. Spin dynamics in magnets 4.1. Critical and low-temperature spin dynamics in ferromagnets 4.2. The correlation function in spin glasses 5. Probing the magnetic properties of superconductors 5.1. The symmetry of the superconducting order parameter in YBa 2 Cu 3 O 6.95 5.2. The vortex state in highly anisotropic high-T c superconductors 5.3. Anisotropy of the magnetic response in UPt 3 6. Summary and perspectives 7. List of works published from July 1993 Appendix A. The magnetic field at the muon site A.1. The magnetic field in the laboratory and crystal reference frames A.2. The Fourier components of the magnetic field A.3. The field distribution at the muon site Appendix B. Muon spin relaxation in a longitudinal field Appendix C. The longitudinal relaxation rate and correlation functions Appendix D. The µSR response function for hard superconductors

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Critical phenomena in dipolar magnets

Cited by 28 publications

References 48 publications

The smectic Z _A phase: Antiferroelectric smectic order as a prelude to the ferroelectric nematic

The smectic Z _A phase: Antiferroelectric smectic order as a prelude to the ferroelectric nematic

Dipolar effects on the critical fluctuations in Fe: Investigation by the neutron spin-echo technique MIEZE

Muon spin rotation and relaxation in magnetic materials

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Critical phenomena in dipolar magnets

Cited by 28 publications

References 48 publications

The smectic Z A phase: Antiferroelectric smectic order as a prelude to the ferroelectric nematic

The smectic Z A phase: Antiferroelectric smectic order as a prelude to the ferroelectric nematic

Dipolar effects on the critical fluctuations in Fe: Investigation by the neutron spin-echo technique MIEZE

Muon spin rotation and relaxation in magnetic materials

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Product

Resources

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The smectic Z _A phase: Antiferroelectric smectic order as a prelude to the ferroelectric nematic

The smectic Z _A phase: Antiferroelectric smectic order as a prelude to the ferroelectric nematic