Electronic and crystallographic structure, hard x-ray photoemission, and mechanical and transport properties of the half-metallic Heusler compound Co2MnGe

Abstract

This work reports on the electronic and crystalline structure and the mechanical, magnetic, and transport properties of the polycrystalline Heusler compound Co 2 MnGe. The crystalline structure was examined in detail by extended x-ray absorption fine-structure spectroscopy and anomalous x-ray diffraction. The compound exhibits a well-ordered L2 1 structure as is typical for Heusler compounds with 2:1:1 stoichiometry. The low-temperature magnetic moment agrees well with the Slater-Pauling rule and indicates a half-metallic ferromagnetic state of the compound, as is predicted by ab initio calculations. Transport measurements and hard x-ray photoelectron spectroscopy were performed to explain the electronic structure of the compound. The obtained valence band spectra exhibit small energy shifts that are the result of the photoexcitation process, whereas electron-electron correlation in the ground state is negligible. The vibration and mechanical properties of the compound were calculated. The observed hardness values are consistent to a covalent-like bonding of Co 2 MnGe.

Electronic structure and optical, mechanical, and transport properties of the pure, electron-doped, and hole-doped Heusler compound CoTiSb

“…Details of the calculations have been reported in previous work. 36 The values of the calculated elastic constants c ij , bulk modulus B, Young's modulus E, rigidity modulus G, Poison's ratio ν, and elastic anisotropy A e are listed in Table II. The values of the calculated elastic constants as well as the elastic anisotropy A e being close to unity satisfy the criteria for mechanical stability of CoTiSb in the cubic system.…”

“…[36][37][38] Most recent studies focused on the optimization of the thermoelectric properties, such as nanostructuring to minimize thermal conductivity, or partial atom substitution to decrease electrical conductivity and/or increase the Seebeck coefficient. Measurements of optical properties have been applied rarely and investigations of mechanical properties have been neglected, so far.…”

Magnetic dichroism study on Mn1.8Co1.2Ga thin film using a combination of x-ray absorption and photoemission spectroscopy

“…Both effects are attributed to multiplet effects and are similar to the behaviour of the Mn states of other Heusler compounds. More details about the multiplet effects are discussed in References [49,44].…”

Probing the electronic states of high-TMR off-stoichiometric Co2MnSi thin films by hard x-ray photoelectron spectroscopy

“…The most pronounced spectral feature at both excitation energies is the maximum of the d states at −1.26 eV. Delocalized Co t 2g minority states form the lower energy part of the maximum while the higher energy part is formed by overlapped Co t 2g and localized Mn e g majority states [43,46,47]. Thus the flat d states of Co are responsible for the half-metallicity in Co β Mn α Si γ .…”