Thermoelectric properties of fe3xcoxsi heusler alloys kohei ishii1, kouta iwasaki1, yuji arita2, masahito yoshino1 takanori nagasaki2 and tsuneo matsui1, 2 1. The first principles study on two alloys of cr2znal and. Heusler alloys have been a significant topic of research due to their unique electronic structure, which exhibits halfmetallicity, and a wide variety of properties such as magnetocalorics, thermoelectrics, and magnetic shape memory effects. Pdf on may 1, 2020, anil aryal and others published mn2fesi. The elements normally associated with the x, y and z are indicated in table1. The similarities in the chemistries of the heusler alloys suggest high mutual solubility, allowing. Department of metallurgical and materials engineering supervisor. Heusler alloy article about heusler alloy by the free. The semi heusler alloys with general formula xyz and the full heusler alloys with x2yz. Any of a group of ferromagnetic nonferrous alloys typically composed of 1825% manganese, 1025% aluminum, and the balance copper explanation of heusler alloy. The poscar file can either be constructed using an existing cif file from an online data. A two dimensional heusler alloy model sciencedirect. Hill 1 suggests that there is a simple explanation of many of the phenomena of the heusler alloys in the allotropic theory of osmond 2. On one hand, a two dimensional model of a heusler alloy may be more tractable than the three dimensional version and may serve to identify key parameters and recognize interesting features.
Page a dissertation submitted in partial fulfillment of the requirements for the degree of doctor of philosophy physics in the university of michigan 2017 doctoral committee. First principles study of full heusler rh tige compound. Ecotopia science institute, nagoya university, nagoya, japan. Especially heusler compounds as halfmetallic ferromagnetic and topological insulators are important in condensed matter science due to their potential in magnetism and as materials for energy conversion. Pdf study of structural, electronic and magnetic properties of. They crystallize in the l2 1 structure which is similar to the c1 b structure butnow the vacant site is occupied by an x atom. Mn 2 yz recently, mnbased heulser alloys with a chemical formula of mn 2 yz have been attracted attention in the field of spintronics because many of them are reported to be halfmetallic ferro or ferrimagnets. Especially heusler compounds as halfmetallic ferromagnetic.
If both the x 2 and y sublattices are empty, the zincblende structure of a iiiv compound semiconductor is formed figure 1a, bottom structure. A collection of various density functional theory dft calculations show that half heusler compounds are predicted to have a lower elastic, shear, and bulk modulus than in. The improvement comes from a simultaneous increase in the seebeck. An antiferromagnetic inverse heusler alloy find, read and cite all the research you need on researchgate. Phase transformation and magnetic properties of multicomponent heusler type alloys kalkanci, mine m. Heusler alloys consist of approximately two parts of copper, one of manganese, and one of tin. The alloys are named after fritz heusler, 19thcentury german mining engineer and chemist.
Fabrication and magnetic properties of structuretunable co2fega. Thin films of the heusler alloys cu2mnal and co2mnsi. The total energy 1etot relative to that of the l21 phase of the alloys studied for different lattice constants a. Among them, some alloys combine the tetragonal distortion with a large magnetic moment and high curie temperature 17, especially, some of them have. Half heusler alloys for efficient thermoelectric power conversion. Heusler alloy, any of the first magnetic alloys composed of metals that, in their pure state, are not magnetic. Especially heusler compounds as halfmetallic ferromagnetic and topological insulators are important in condensed matter science due to their potential in. Perpendicular magnetic anisotropy in heusler alloy films. However, there are yet to be any reports of this 100% spin polarisation experimentally. This discovery led to a general investigation of the magnetic properties of manganese alloys.
Exchange interactions and temperature dependence of. Especially heusler compounds as halfmetallic ferromagnetic and topological. Heusler alloys ha are a class of materials which may be metals, semiconductors or semimetals, most of them being ferromagnets. Co and in doped nimnga magnetic shape memory alloys. Synthesisandcharacterizationof half4metallicheusler.
Heusler article about heusler by the free dictionary. Heusler alloys are named for the german mining engineer and chemist friedrich heusler who investigated cumnal alloys around 1900 1. These hhs have total valenceelectron countvec equal to 18 in theirprimitive unitcell. Heusler alloy is ternary x2yz compounds with l21 structure. Heusler alloys have been a significant topic of research due to their unique electronic structure, which exhibits halfmetallicity, and a wide variety of properties such as magnetocalorics. Modelling the phase diagram of magnetic shape memory. Poon1,a 1 department of physics, university of virginia, charlottesville, virginia 229044714. Avik ghoshs group at the university of virginia, provides information on three families of heusler alloys, full heuslers a2bc, half heuslers abc and inverse heuslers abac. Heusler alloy definition is a magnetic alloy composed of the nonmagnetic metals copper, manganese, and tin approximately in the proportions cu2mnsn.
The semi and full heusler alloys are characterized by the c1b and l21 structures, respectively. Especially, focus is given to binary heusler alloys by replacing the second element in the ternary heusler alloys with the third one, e. Novel materials for energy and spintronic applications article pdf available in semiconductor science and technology 276 june 2012 with 4,414 reads how we measure. For each of these families, we provide calculations for numerous systems. G suresh 1,2magnetic materials lab, indian institute of technology bombay, mumbai, india email. Heusler reported that he had accidentally discovered that certain manganese alloys were magnetic. Properties, growth, applications springer series in materials science on free shipping on qualified orders. Design of compensated ferrimagnetic heusler alloys for. Structural properties of magnetic heusler alloys iopscience. In 1903 heusler first reported that mncu bronze can be alloyed with sn, al, as, sb, bi or b to produce ferromagnetic alloys even though none of the constituent elements is itself ferromagnetic. The method includes combining and arc melting constituent elements of the thermoelectric material to form a liquid alloy of the thermoelectric material and casting the liquid alloy of the thermoelectric material to form a solid casting of the thermoelectric material. Although heusler alloys have been known for more than a century, but since the last decade there has been a quantum jump in research in this area.
Halfheusler alloys as promising thermoelectric materials. Some new applications of ha in spintronics and microelectromagnetic actuators require their preparation in the form of thin films. Heusler alloys properties, growth, applications claudia. Heusler reported that it was possible to make ferromagnetic alloys from nonferromagnetic constituents coppermanganese bronze and group b elements such as aluminium and tin. Heusler magnetic alloys show these properties only in off stoichiometry. Many hhs have been studied over the years with the main focus on mnisn m ti, zr, hf 7,9,11. Among the heusler alloys, mn2yz based members y being a 3d or 4d transition. Professor ctirad uher, chair assistant professor emmanouil kioupakis associate professor lu li. Realization of multifunctional shapememory ferromagnets. This feature predicts a discovery of new catalysts, and enables them to substitute each other e. Ternary heusler compounds have the general formula x 2 yz, where x and y are transition metals and z is a main group element. Computational investigation of heusler alloys for spintronic.
Surface properties of the halfand fullheusler alloys. Magnetically driven actuator materials, such as the ternary and intermetallic heusler alloys with composition, are studied within the densityfunctional theory dft with the generalized gradient approximation gga for the electronic exchange and correlation. Half heusler alloys as promising thermoelectric materials by alexander a. Structure and magnetic properties of heusler alloy fe niz. The typical regular l2 1 or inverse heusler structures provide two distinct crystallographic sites for the iron atoms which can be well distinguished as their isomer shifts and hyperfine fields are different.
Structure and magnetic properties of heusler alloy fe niz z. First principles electronic structure and magnetic properties of. This book gives an overview of the physics of heusler compounds ranging from fundamental properties of these alloys to their applications. The elastic modulus values of half heusler alloys range from 83 to 207 gpa, whereas the bulk modulus spans a tighter range from 100 gpa in hfnisn to gpa in ticosb. Optimisation of heusler alloy thin films for spintronic. However, there are yet to be any reports of this 100% spin polarisation. Since, the prediction of hmf nature in nimnsb 6, heusler alloys have received a special attention due to the reasons mentioned above. Recently, we find a good method to develop new materials with half metallicity is to combine two. A number of cobased heusler alloys are predicted to be halfmetallic ferromagnets that would theoretically provide 100% spin polarisation at the fermi energy. Department of materials, physics and energy engineering, nagoya university, nagoya, japan 2. Mekhrabov september 2011, 77 pages many cobased heusler alloys with the stoichometric composition x 2 yz are ideal. In 1903 heusler 03 h 1 first reported that mncu bronze can be alloyed with sn, al, as, sb, bi or b to produce ferromagnetic alloys even though none of the constituent elements is itself. Further investigations showed that the magnetic properties of these alloys are related to their chemical, l2 1, structure, and to the ordering of the manganese atoms on an f. Structure, properties and applications opens by analyzing how by substituting nickel for iron, another heusler alloy emerges, fe2mnga, with much richer structural and magnetic properties than ni2mnga and a large ferromagnetic shape memory performance.
In addition, due to the complexity of the threedimensional heusler alloys, the interplay of magnetism and chemical order, has been addressed only in a reduced number of theoretical studies 11, 12. In the large family of heusler alloys, generally co based alloys show. Heusler reported that it was possible to make ferromagnetic alloys from nonferromagnetic constituents coppermanganese bronze and group b. Thermoelectric materials and methods of making thermoelectric materials having a nanometer mean grain size less than 1 micron.
Among the fe 2based heusler alloys, the fe 2crz z is the main group. At the stoichiometric composition, full heusler alloys x2yz and semi heusler alloys xyz crystallize in l21 and c1b structures see. Us20120326097a1 halfheusler alloys with enhanced figure of. Heusler alloy catalysts have also recently been studied by other groups. Direct observation of halfmetallicity in the heusler. Heusler alloys show remarkable properties, such as ferromagnetic shape memory effect, magnetocaloric effect, half metallicity, and most recently it has been shown that it can be used for direct conversion of heat into electricity. The database, developed by william butlers group at the university of alabama and prof.
Introduction in 1996, pioneering work by ullakko, and ohandley and his group in collaboration with kokorin introduced a new magnetoelastic effect, the magnetic field induced variant reorientation mir in ni2mnga heusler alloys 1. Novel halfmetallic and spingapless heusler compounds by. Among these, heusler alloys have a special importance due to their higher curie temperatures t c and tunable electronic structure 2,3,6. Many such heusler alloys are explored and reported to be spintronic 5, 6 materials.
Ferromagnetic shape memory heusler alloys scientific. Heusler compounds are a large family of binary, ternary and quaternary. These alloys were interesting because some of them were ferromagnetic even though their constituent atoms were nonferromagnetic as elements. These heusler alloys present an interesting class of ferromagnetic materials for spintronic applications since they are predicted to be spin gapless semiconductors and have halfmetallic properties with 100 % spin polarization at the fermi level. Candanthis content was downloaded from ip address 207. Heusler alloys comprise an extensive family with diverse physical properties1. Spinorbit interaction, halfmetals, halfheusler alloys, licras, limnsi. The first principles study on two alloys of cr2znal and cr2agal figure 3. Combining experimental analysis and abinitio calculations, we succeeded to model the evo lution of. Pdf the structural, electronic and magnetic properties of halfheusler cofein and fullheusler co2fein alloys have been investigated by. The heusler alloys are categorized into two distinct groups by their crystalline structures. Co2fesi, a heusler alloy with the highest magnetic moment per unit cell and the highest curie temperature, has largely been described theoretically as a halfmetal. For the half heusler alloy xyz with the c1 b crystal structure, the x 1 sublattice is empty.
Structural properties of magnetic heusler alloys 2019 10. These peaks merge to form a more prominent one in magnitude in case of. Heusler alloy is also a typical object for studying the ordered atomic configuration and magnetic coupling for intermetallic compounds2. Heusler alloys hhs from the view point of their thermoelectric prospects. Pdf highspin polarization of heusler alloys claudia. Miroshkina et almagnetic, electronic, mechanic, anisotropic elastic and vibrational properties of antiferromagnetic ru2tga t cr, mn, and co heusler alloys a. The second family of heusler alloys are the socalled full heusler alloys and they have the x 2yz formula. As the maturity of these materials grows and commercial applications become more nearterm, the mechanical properties of these materials become an. Being heusler alloys, they both contained manganese and two other elements. Given the highly ordered l2 1 structure, both heusler alloys are strong ferromagnets with magnetic moments and ferromagnetic curie temperatures of 3. He had a helmet of bronze on his head, and he was armed with a coat of mail, and the weight of the coat was five thousand shekels of bronze. Heusler sdiscoverythatitispossibletoproducefromsocalled. This database provides information on three families of heusler alloys, full heuslers a 2 bc, half heuslers abc and inverse heuslers abac. Stateoftheart te figure of merit of halfheusler materials.
Full heusler alloys with l21 structure and cb1 structure have been studied 2, 3, 4 mainly for its half metallic character and some of them are found to be ferromagnetic with 100 % spin polarized. There are so many possible sets of x, y,andz figure 2. Ferromagnetic heusler alloys experienced a striking. They have long been known as magnetic materials, but can also be. Fraunhofer ipm has installed a semiautomatic module fabrication for this type of thermoelectric modules in order to develop teg demonstrators and prototype. Therefore, synthesizing and investigating new systems becomes an attractive subject for investigators working in this field. The x and y elements come from the transition metal group, whereas the z component is the element of the iiiv group. Half heusler alloys for efficient thermoelectric power. Alloys and there came out from the camp of the philistines a champion named goliath, of gath, whose height was six cubits and a span. Heusler alloys max planck institute for chemical physics. Since the prediction of the half heusler halfmetal nimnsb with 100% spin polarization2,many studies have been devoted to searching for and verifying heuslers with halfmetallicity. Typically, x and y are transition metals in groups 3. This conclusion, however, disagrees with point contact andreev reflection pcar.
Heusler alloy database electrical and computer engineering. Libased halfheusler alloys have attracted much attention due to their potential applications in. While turning a certain alloy in a lathe, he had noticed that the turnings adhered to the tool. Heusler alloys the heusler compounds are an exciting class of intermetallics due to their ability to adopt a wide range of tunable electrical and magnetic properties, including metallicity, half metallic ferromagnetism, superconductivity, and narrow band gap semiconducting behavior with large thermoelectric power factors. The calculated total density of states dos is shown in figure 2. Heusler alloys properties, growth, applications claudia felser.
Heusler compounds are magnetic intermetallics with facecentered cubic crystal structure and a composition of xyz halfheuslers or x 2 yz fullheuslers, where x and y are transition metals and z is in the pblock. Here we restrict to heusler alloys with mn as its only magnetic component. Heusler alloys are one of the leading candidate material classes for achieving high spin polarisation. May 30, 2014 ferromagnetic thin films of heusler compounds are highly relevant for spintronic applications owing to their predicted halfmetallicity, that is, 100% spin polarization at the fermi energy. Pdf halfmetallic properties in the new ti2nib heusler alloy. In the past, heusler compounds were often understood as intermetallic alloys, although the description as an intermetallic compound is more appropriate due to their characteristic atomic order. Simple rules for the understanding of heusler compounds. Heusler alloy definition of heusler alloy by merriamwebster. Wo2012087931a2 halfheusler alloys with enhanced figure of. Many of these compounds exhibit properties relevant to spintronics, such as magnetoresistance, variations of the hall effect, ferro, antiferro, and ferrimagnetism, halfand. Spintronic properties and stability of the halfheusler alloys. The majority spin band structures of cr2agal with f43m crystal structure.