Metamagnetism

About: Metamagnetism is a research topic. Over the lifetime, 2023 publications have been published within this topic receiving 38108 citations.

Magnetic surface domain imaging of uncapped epitaxial FeRh(001) thin films across the temperature-induced metamagnetic transition

Abstract: The surface magnetic domain structure of uncapped epitaxial FeRh/MgO(001) thin films was imaged by in-situ scanning electron microscopy with polarization analysis (SEMPA) at various temperatures between 122 and 450 K. This temperature range covers the temperature-driven antiferromagnetic-to-ferromagnetic phase transition in the body of the films that was observed in-situ by means of the more depth-sensitive magneto-optical Kerr effect. The SEMPA images confirm that the interfacial ferromagnetism coexisting with the antiferromagnetic phase inside the film is an intrinsic property of the FeRh(001) surface. Furthermore, the SEMPA data display a reduction of the in-plane magnetization occuring well above the phase transition temperature which, thus, is not related to the volume expansion at the phase transition. This observation is interpreted as a spin reorientation of the surface magnetization for which we propose a possible mechanism based on temperature-dependent tetragonal distortion due to different the...

Magnetoelastic effects in ErNi2B2C single crystal: probing the H-T phase diagram

Abstract: Using a capacitive dilatometer we investigated the magnetoelastic behaviour of single-crystalline ErNi2B2C in the temperature range 1. 8K T 16 K and for external magnetic field in the tetragonal ab-plane µ0H 6T . For T TN = 6.4 K the longitudinal magnetostriction coefficient is negative, whereas the transverse one is positive. The thermal evolution of the lattice distortion e γ = (λ⊥ − λ� )/ √ 2 is in agreement with that of the previously reported spontaneous tetragonal-to-orthorhombic distortion determined by neutron diffraction. The behaviour is influenced by the distribution of the magnetic domains in the crystal. The H –T phase diagram, constructed from the magnetostriction curves, shows the well-known cascade of metamagnetic transitions between several phases (antiferromagnetic AF1, ferrimagnetic F1, F2) in the field range 0 <µ 0 H< 2.1 T below TN . On the basis of a Hamiltonian consisting of an exchange, a crystal-field, a Zeeman, and a magnetoelastic term, we were able to reproduce reasonably well the H –T phase diagram as well as various forced magnetostriction curves. (Some figures in this article are in colour only in the electronic version)

Mixed magnetic phases in tetragonal

Abstract: A careful analysis of neutron diffraction experiments under magnetic field performed on a single crystal of tetragonal is presented. It shows that the zero-field-low-temperature magnetic phase is not the natural compensated antiphase structure proposed so far for the Q = (3/13, 0, 0) propagation vector, but a mixed phase where the moment of two of the 26 Tb sites of the unit cell vanishes. The magnetic structures of the first three field induced phases of the multistep metamagnetic process agree with previous analysis whereas the fourth field induced phase is not the non-mixed proposed one but a mixed one with two zero moments as in zero field. Contrary to previous interpretations, the transition at 4.7 K observed by specific heat and susceptibility corresponds to the change of the magnetic structure from the mixed low-temperature one to a slightly modulated non-mixed one. Numerical simulation allowed us to account for the main properties observed and emphasizes the crucial role of the crystal field.

Metamagnetism of CoS 2 under High Pressure and in Co(SxSe 1- x ) 2

Abstract: The effects of external pressure and the substitution of S by Se on the ferromagnetic phase transtion in CoS 2 were studied by magnetization measurements. Both operations reduced T c , made the magnetic phase transition discontinuous and gave rise to the metamgnetic transition immediately above T c . In terms of the phenomenological Landau theory, our experimental results are consistently interpreted on the basis of the variation of the fourth coefficient ( F 4 ) from a small positive value through zero to a negative value by varying Se-concentration or applying pressure. The appearance of weak metamagnetic transition in CoS 2 at ambient pressure also supports that F 4 is nearly equal to zero under the external field. Therefore, the anomalous critical exponents in CoS 2 reflect the tricritical behavior, as in the previous argument.

Strong Longitudinal Magnetic Fluctuations Near Critical End Point in UCoAl: A 59Co-NMR Study

Abstract: We report 59 Co-NMR measurements in UCoAl where metamagnetism occurs owing to the enhancement of ferromagnetism by a magnetic field. The metamagnetic transition from a paramagnetic (PM) state to a ferromagnetic state is a first-order transition at low temperatures, but it changes to a crossover at high temperatures on crossing the critical end point (CEP) at T CEP ∼12 K. The contrasting behavior between the relaxation rates 1/ T 1 and 1/ T 2 suggests that the longitudinal magnetic fluctuation of the U moments is strongly enhanced, especially near the CEP. A wide diffusion of the fluctuation from the CEP can be confirmed even in the PM state where the magnetic transition does not occur.