Le métamagnétisme

Becquerel, Jean; Handel, J. van den

doi:10.1051/jphysrad:0193900100101000

Cited by 25 publications

(10 citation statements)

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“…to an anomalous increase of the susceptibility, and finally -at high fields -to a saturation of the magnetization. Such a behavior was indeed observed by Becquerel and van den Handel in 1939 [3] in the mineral mesitite (carbonate of Fe and Mg) at low temperatures. Not being aware of Landau's or Néel's work they could not explain their observation in terms of ferro-and paramagnetism, and therefore suggested for it the name metamagnetism [4].…”

Section: Introductionsupporting

confidence: 76%

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Correlated-electron theory of strongly anisotropic metamagnets

et al. 1997

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The microscopic origin of metamagnetism and metamagnetic transitions in strongly anisotropic antiferromagnets is investigated within a quantum mechanical theory of correlated electrons. To this end the Hubbard model with staggered magnetization m_st along an easy axis e in a magnetic field H || e is studied both analytically and numerically within the dynamical mean field theory (DMFT). At intermediate couplings the self-consistent DMFT equations, which become exact in the limit of large coordination number, are solved by finite temperature Quantum Monte Carlo techniques. The temperature and magnetic field dependence of the homogeneous and staggered magnetization are calculated and the magnetic phase diagram is constructed. At half filling the metamagnetic transitions are found to change from first order at low temperatures to second order near the N'eel temperature, implying the existence of a multicritical point. Doping with holes or electrons has a strong effect: the system becomes metallic, the electronic compressibility increases and the critical temperatures and fields decrease. These results are related to known properties of insulating metamagnets such as FeBr_2, metallic metamagnets such as UPdGe, and the giant and colossal magnetoresistance found in a number of magnetic bulk systems.Comment: 14 pages including 10 figures, RevTeX, using psfig and epsf macro

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Section: Introductionsupporting

confidence: 76%

“…The self-consistency is obtained iteratively as follows: the Green function G (omitting indices) is calculated from some initial self energy, e.g. Σ ≡ 0, by the Dyson equation (3). Now the new Green function G new is determined by solving (4) with the QMC method.…”

Section: Dynamical Mean-field Theory (D → ∞)mentioning

confidence: 99%

Correlated-electron theory of strongly anisotropic metamagnets

et al. 1997

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“…The term metamagnetism, possibly coined by Kramers as a joke, was used to describe the bizarre properties of certain magnetic materials that have been investigated for more than 100 years. They appeared to be paramagnetic or antiferromagnetic in the ground state, but ferromagnetic in applied fields [1][2][3] and could be pictured as an Hegelian synthesis step reconciling opposing tendencies of magnetic behavior. Metamagnetism now labels a sudden rise or cross-over of the magnetization under applied field and is observed in various classes of materials.…”

Section: Introductionmentioning

confidence: 99%

Metamagnetic texture in a polar antiferromagnet

Sokolov¹,

Kikugawa²,

Helm³

et al. 2019

Nat. Phys.

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The notion of a simple ordered state implies homogeneity. If the order is established by a broken symmetry, elementary Landau theory of phase transitions shows that only one symmetry mode describes this state. Precisely at points of phase coexistence domain states formed of large regions of different phases can be stabilized by long range interactions. In uniaxial antiferromagnets the so-called metamagnetism is an example of such a behavior, when an antiferromagnetic and field-induced spin-polarized paramagnetic/ferromagnetic state co-exist at a jump-like transition in the magnetic phase diagram. Here, combining experiment with theoretical analysis, we show that a different type of mixed state between antiferromagnetism and ferromagnetism can be created in certain acentric materials. In the small-angle neutron scattering experiments we observe a field-driven spin-state in the layered antiferromagnet Ca3Ru2O7, which is modulated on a scale between 8 and 20 nm and has both antiferromagnetic and ferromagnetic parts. We call this state a metamagnetic texture and explain its appearance by the chiral twisting effects of the asymmetric Dzyaloshinskii-Moriya (DM) exchange.The observation can be understood as an extraordinary coexistence, in one thermodynamic state, of spinorders belonging to different symmetries. Experimentally, the complex nature of this metamagnetic state is demonstrated by measurements of anomalies in electronic transport which reflect the spin-polarization in the metamagnetic texture, determination of the magnetic orbital moments, which supports the existence of strong spin-orbit effects, a pre-requisite for the mechanism of twisted magnetic states in this material. Our findings provide an example of a rich and largely unexplored class of textured states. Such textures mediate between different ordering modes near phase co-existence, and engender extremely rich phase diagrams.

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“…So the Fe 2+ ions can adopt a high spin (HS, S = 2) or low spin (LS, S = 0) state. Magnetic susceptibility and neutron-diffraction experiments have indicated that FeCO 3 was an antiferromagnetic (AFM) compound with a low Néel temperature of 38 K [4][5][6][7][8]. All the magnetic moments (Fe 2+ ion) are ferromagnetically (FM) coupled inside a (0 0 0 1) Fe plane, whereas neighboring planes along the c axis are antiferromagnetically coupled.…”

Section: Introductionmentioning

confidence: 99%