Search results for "Magnetism"

Magnetic Heusler Compounds

2013

Abstract Heusler compounds are a remarkable class of intermetallic materials with 1:1:1 (often called Half-Heusler) or 2:1:1 composition comprising more than 1500 members. New properties and potential fields of applications emerge constantly; the prediction of topological insulators is the most recent example. Surprisingly, the properties of many Heusler compounds can easily be predicted by the valence electron count or within a rigid band approach. The wide range of the multifunctional properties of Heusler compounds is reflected in extraordinary magnetooptical, magnetoelectronic, and magnetocaloric properties. Co 2 -Heusler compounds are predicted and proven half-metallic ferromagnets sho…

The difference of crystal fields in ErAl2 and La0.9Er0.1Al2

1978

Abstract Inelastic neutron scattering experiments have been carried out on polycrystalline ErAl2 and on the related pseudobinary compound La0.9Er0.1Al2 in the paramagnetic phase. For ErAl2 the parameters of the cubic crystal field could uniquely be determined as x=+0.16 and W=−0.030 meV. The results on the dilute sample are different from this and are thought to be due effective charges of Er and La being not equivalent.

Magnetoresistance and Phase Diagram of Thin-Film UNi2Al3

2011

We study the dc resistivity of UNi2Al3 thin films as a function of temperature and magnetic field. We focus on the temperature range around the antiferromagnetic transition (TN \approx 4 K in zero applied field). From a clear signature of TN in the dc resistance along the crystallographic a-direction, we extract the shape of the magnetic phase diagram. Here we find quantitative differences in comparison to previous studies on bulk crystals.

Mechanism for ultrafast electric-field driven skyrmion nucleation

2021

We show how a Dzyaloshinskii-Moriya interaction can be generated in an ultrathin metal film from a femtosecond pulse in electric field. This interaction does not require structural inversion-symmetry breaking, and its amplitude can be tuned depending on the amplitude of the field. We perform first-principles calculations to estimate the strength of the field-induced magnetoelectric coupling for ferromagnetic Fe, Co, and Ni, and antiferromagnetic Mn, as well as FePt and MnPt alloys. Last, using atomistic simulations, we demonstrate how an isolated antiferromagnetic skyrmion can be coherently nucleated from the collinear background by an ultrashort pulse in electric field on a hundred-femtose…

An Ising ferromagnet with an antiferromagnetic surface layer: A simple model for magnetic surface reconstruction

1985

Simple cubic Ising lattices are studied by Monte Carlo simulation, using a thin film geometry (usually 40 atomic layers thick), with nearest neighbour ferromagnetic exchange J in the bulk and nearest neighbour antiferromagnetic interaction Js between surface spins. Applying a technique of preferential sampling in the surface layers, we investigate the ordering for a variety of values of JsJ and for various temperatures. For JsAF < Js < − 0.25J (where JsAF ≈ − 2.01J) ferromagnetic ordering occurs at a higher temperature than the antiferromagnetic surface ordering, while for − 0.25J < Js no antiferromagnetic long range order is possible. For Js < JsAF the surface transition occurs at a higher…

A neutron scattering study of the magnetic properties of PrSn3

1988

The intermetallic compound PrSn3 has been studied by elastic and inelastic neutron scattering. The paramagnetic phase shows overdamped crystal field excitations and an anisotropic distribution of the diffuse magnetic intensity. The dispersion relation of the excitations of the antiferromagnetic phase has been determined. The results are analyzed in terms of an anisotropic exchange coupling.

Magnetic Skyrmions: Current-Induced Skyrmion Generation through Morphological Thermal Transitions in Chiral Ferromagnetic Heterostructures (Adv. Mate…

2018

Electronic, structural, and magnetic properties of the half-metallic ferromagnetic quaternary Heusler compounds CoFeMnZ(Z=Al, Ga, Si, Ge)

2011

The quaternary intermetallic Heusler compounds CoFeMn$Z$ ($Z=\text{Al}$, Ga, Si, or Ge) with $1:1:1:1$ stoichiometry were predicted to exhibit half-metallic ferromagnetism by ab initio electronic structure calculations. The compounds were synthesized using an arc-melting technique and the crystal structures were analyzed using x-ray powder diffraction. The electronic properties were investigated using hard x-ray photoelectron spectroscopy. The low-temperature magnetic moments, as determined from magnetization measurements, follow the Slater-Pauling rule, confirming the proposed high spin polarizations. All compounds have high Curie temperatures, allowing for applications at room temperature…

Alloying experiments on heavy fermion compounds

1990

Abstract This paper is intended to demonstrate the usefulness of controlled alloying for the understanding of heavy-fermion physics: (1) Th-substitution for Ce in CeCu2Si2 emphasizes the dominating role of the dopant-induced strain fields in generating incoherent scattering and pair breaking, (2) replacement of Cu by Ni in Ce(Cu1-xNix)2Ge2 leads to phenomena which are interpreted as derived from a transition between local-moment and itinerant heavy-fermion magnetism, and (3) increasing Cu concentration in UCu4+xAl8-x is accompanied by an antiferromagnetic to nonmagnetic transition near xcr = 1.5 similar to what has been found before for several Ce-based systems. A heavy Fermi-liquid phase w…

Monte Carlo Simulations of Body Centered Cubic Alloys

1994

We illustrate the use of Monte Carlo simulations in the study of order-disorder phenomena in metallic alloys by presenting detailed work on a fairly realistic lattice model for iron aluminum. The model has been constructed based on recent measurements of effective interaction parameters and includes a description of the magnetism of iron within a Heisenberg Hamiltonian. We show that it reproduces the bulk phase diagram in a qualitatively correct way. Then internal antiphase boundaries and free surfaces in the (100)-direction are studied. An interfacial roughening transition is predicted as well as critical broadening of the profiles as the bulk approaches a second order transition. Nonstoec…