The electronic structures of four Laves phase iron compounds (e.g. YFe$_2$, ZrFe$_2$, LuFe$_2$ and HfFe$_2$) have been calculated by the state-of-the-art full potential electronic structure code. The magnetic moments collapse under hydrostatic pressure. This feature is found to be universal in these materials. Its electronic origin is provided by the sharp peaks in the density of states near the Fermi level. It is shown that a first order quantum phase transition can be expected under pressure in Y(Zr, or Lu)Fe$_2$, while a second order one in HfFe$_2$. The bonding characteristics are discussed to elucidate the equilibrium lattice constant variation. The large spontaneous volume magnetostriction gives one of the most important character of these compounds. Invar anomalies in these compounds can be partly explained by the current work when the fast continuous magnetic moment decrease at the decrease of the lattice constant was properly considered. This work may remind the experimentalists of these "old" compounds and exploration of the quantum properties under high pressures are greatly encouraged.
We report the magnetization ($M$) and magnetoresistance (MR) results of HoAl$_2$ single crystals oriented along $<100>$ and $<110>$ directions. Although HoAl$_2$ has cubic Laves phase structure, a large anisotropy is observed in $M$ and MR results below Curie temperature ($T_C$) at 31.5 K. A satisfactory correlation between magnetic entropy change ($ΔS_M$) and MR could be established along $<110>$ direction and in $<100>$ direction except for the temperature ($T$) region, around which spin reorientation takes place. Large inverse magnetocaloric effect is observed at low-$T$ which is associated…
The temperature ($T$) as a function of pressure ($P$) phase diagram is reported for the cubic Laves phase compound Au$_2$Pb, which was recently proposed to support linearly dispersing "topological" bands, together with conventional quadratic bands. At ambient pressure, Au$_2$Pb exhibits several structural phase transitions at $T_1$ $=$ 97 K, $T_2$ $=$ 51 K, and $T_3$ $=$ 40 K with superconductivity below $T_{\rm{c}}$ $=$ 1.2 K. Applied pressure results in a rich phase diagram where $T_1$, $T_2$, and $T_3$ evolve strongly with $P$ and a new phase is stabilized for $P$ $>$ 0.64 GPa that also sup…
The Laves phase skeleton in cast Mg-Al-Ca alloys is known to provide considerable strengthening. Laves phases such as CaMg$_2$ (C14), Ca(Al,Mg)$_2$ (C36), and CaAl2 (C15) have high melting points, high hardness at room and elevated temperatures, but unfortunately are inherently brittle. Mg-Al-Ca alloys thus have good creep properties but limited ductility. An understanding of the co-deformation behaviour of $α$-Mg and Laves phases is essential for optimising the strength-ductility balance of these alloys. Here, we study the mechanical behaviour of a Mg-4.65Al-2.82Ca alloy using micropillar com…
Metallic Bonding-Driven Elastic Softness and Optical Response in the Mg-Rich Laves-Phase LaMg2
Pabna Textile Engineering College, Bangladesh University of Textiles（帕尔纳纺织工程学院，孟加拉国纺织大学）；EcoBengal Centre for Materials and Energy Research（生态孟加拉材料与能源研究中心）；Bangladesh Atomic Energy Regulatory Authority (BAERA)（孟加拉国原子能监管局）；Department of Physics, University of Barishal（巴里萨尔大学物理系）；Department of Electrical and Mechanical Engineering, Nagoya Institute of Technology（名古屋工业大学电气与机械工程系）；School of Materials Science and Engineering, Faculty of Science, University of New South Wales（新南威尔士大学理学院材料科学与工程系）
Hydrogen diffusion in TiCr$_2$H$_x$ Laves phases: A combined ab initio and machine-learning-potential study
University of Stuttgart（斯图加特大学）；Ruhr-Universität Bochum（波鸿鲁尔大学）；Max-Planck-Institut for Sustainable Materials（马克斯·普朗克可持续材料研究所）；Kyushu University（九州大学）；Mitsui Chemicals, Inc.（三井化学株式会社）
We study the structural stability and dynamical properties of Ar(H2)2 under pressure using first-principles and ab initio molecular dynamics techniques. At low temperatures, Ar(H2)2 is found to stabilize in the cubic C15 Laves structure (MgCu2) and not in the hexagonal C14 Laves structure (MgZn2) as it has been assumed previously. Based on enthalpy energy and phonon calculations, we propose a temperature-induced MgCu2 -> MgZn2 phase transition that may rationalize the existing discrepancies between the sets of Raman and infrared vibron measurements. Our AIMD simulations suggest that the meltin…
Electronic structure and magnetic properties of ZrFe$_2$ with a cubic Laves phase are investigated by calculations based on the density functional theory. The total magnetic moment (m) of 3.14 $μ_B$ per formula unit (\emph{f.u.}) is obtained at the experimental lattice constant (7.06 Å), which is larger than 3.06 $μ_B$/\emph{f.u.} obtained at the theoretical equilibrium lattice constant (6.85 Å). The localized $3d$ magnetic moment is in negative diffusive sp background moment. We predict a two-step magnetic collapse under pressure: one is from 3.06 $μ_B$/\emph{f.u.} to 1.26 $μ_B$/\emph{f.u.} a…
Influence of Ni substitution on the phase transitions and magnetocaloric effect of NdCo2 at cryogenic temperatures
Institute for Energy Technology (IFE)（能源技术研究所）；Technical University of Darmstadt（达姆施塔特工业大学）；Helmholtz-Zentrum Dresden-Rossendorf（亥姆霍兹德累斯顿-罗斯多夫中心）；Technische Universität Dresden（德累斯顿工业大学）；Paul Scherrer Institute (PSI)（保罗谢勒研究所）
The dielectric properties of tantalum doped BaTi0.85Zr0.15O3 were investigated. The conventional solid state reaction method was used to make the ceramic samples. The composition was close to the pinch point of the three structure phase transitions in BaTiO3. Powder X-ray diffraction result indicated that the samples were in very slightly distorted rhombohedral structure at room temperature, and the dielectric measurement showed only cubic-to-rhombohedral phase transition occurred. Instead of a sharp peak characteristic of a ferroelectric (FE) transition, the large dielectric response was simi…
We show that the magnetism of double perovskite AFe_{1/2}M_{1/2}O_3 systems may be described by the Heisenberg model on the simple cubic lattice, where only half of sites are occupied by localized magnetic moments. The nearest-neighbor interaction J_1 is more than 20 times the next-nearest neighbor interaction J_2, the third-nearest interaction along the space diagonal of the cube being negligible. We argue that the variety of magnetic properties observed in different systems is connected with the variety of chemical ordering in them. We analyze six possible types of the chemical ordering in 2…
