In materials science, galfenol is the general term for an alloy of iron and gallium. The name was first given to iron-gallium alloys by United States Navy researchers in 1998 when they discovered that adding gallium to iron could amplify iron's magnetostrictive effect up to tenfold. Galfenol is of interest to sonar researchers because magnetostrictor materials are used to detect sound, and amplifying the magnetostrictive effect could lead to better sensitivity of sonar detectors. [1] Galfenol is also proposed for vibrational energy harvesting, actuators for precision machine tools, active anti-vibration systems, and anti-clogging devices for sifting screens and spray nozzles. Galfenol is machinable and can be produced in sheet and wire form. [2] [3]
In 2009, scientists from Virginia Polytechnic Institute and State University, and National Institute of Standards and Technology (NIST) used neutron beams to determine the structure of galfenol. They determined that the addition of gallium changes the lattice structure of the iron atoms from regular cubic cells to one in which the faces of some of the cells become slightly rectangular. The elongated cells tend to clump together in the alloy, forming localized clumps within the material. These clumps have been described by Peter Gehring of the NIST Center for Neutron Research as "something like raisins within a cake". [1] It has also been proposed that there is an intrinsic mechanism generating this enhanced magnetostriction, which has its origins in the electronic structure of the material as described by density functional theory. [4] It is understood that the addition of gallium to pure iron alters the electronic structure and atomic arrangements in the material in such a way as to enhance the material's magnetoelastic constant. [5]
Gallium is a chemical element; it has symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, gallium is in group 13 of the periodic table and is similar to the other metals of the group.
Magnetostriction is a property of magnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of materials' magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ. The effect was first identified in 1842 by James Joule when observing a sample of iron.
An amorphous metal is a solid metallic material, usually an alloy, with disordered atomic-scale structure. Most metals are crystalline in their solid state, which means they have a highly ordered arrangement of atoms. Amorphous metals are non-crystalline, and have a glass-like structure. But unlike common glasses, such as window glass, which are typically electrical insulators, amorphous metals have good electrical conductivity and can show metallic luster.
Magnetic shape memory alloys (MSMAs), also called ferromagnetic shape memory alloys (FSMA), are particular shape memory alloys which produce forces and deformations in response to a magnetic field. The thermal shape memory effect has been obtained in these materials, too.
Tunnel magnetoresistance (TMR) is a magnetoresistive effect that occurs in a magnetic tunnel junction (MTJ), which is a component consisting of two ferromagnets separated by a thin insulator. If the insulating layer is thin enough, electrons can tunnel from one ferromagnet into the other. Since this process is forbidden in classical physics, the tunnel magnetoresistance is a strictly quantum mechanical phenomenon, and lies in the study of spintronics.
Boron carbide (chemical formula approximately B4C) is an extremely hard boron–carbon ceramic, a covalent material used in tank armor, bulletproof vests, engine sabotage powders, as well as numerous industrial applications. With a Vickers hardness of >30 GPa, it is one of the hardest known materials, behind cubic boron nitride and diamond.
Terfenol-D, an alloy of the formula TbxDy1−xFe2 (x ≈ 0.3), is a magnetostrictive material. It was initially developed in the 1970s by the Naval Ordnance Laboratory in the United States. The technology for manufacturing the material efficiently was developed in the 1980s at Ames Laboratory under a U.S. Navy-funded program. It is named after terbium, iron (Fe), Naval Ordnance Laboratory (NOL), and the D comes from dysprosium.
A ferrite is an iron oxide-containing magnetic ceramic material. They are ferrimagnetic, meaning they are attracted by magnetic fields and can be magnetized to become permanent magnets. Unlike many ferromagnetic materials, most ferrites are not electrically conductive, making them useful in applications like magnetic cores for transformers to suppress eddy currents.
Heusler compounds are magnetic intermetallics with face-centered cubic crystal structure and a composition of XYZ (half-Heuslers) or X2YZ (full-Heuslers), where X and Y are transition metals and Z is in the p-block. The term derives from the name of German mining engineer and chemist Friedrich Heusler, who studied such a compound (Cu2MnAl) in 1903. Many of these compounds exhibit properties relevant to spintronics, such as magnetoresistance, variations of the Hall effect, ferro-, antiferro-, and ferrimagnetism, half- and semimetallicity, semiconductivity with spin filter ability, superconductivity, topological band structure and are actively studied as thermoelectric materials. Their magnetism results from a double-exchange mechanism between neighboring magnetic ions. Manganese, which sits at the body centers of the cubic structure, was the magnetic ion in the first Heusler compound discovered. (See the Bethe–Slater curve for details of why this happens.)
Natalia Dubrovinskaia is a Swedish geologist of Russian origin.
The inverse magnetostrictive effect, magnetoelastic effect or Villari effect, after its discoverer Emilio Villari, is the change of the magnetic susceptibility of a material when subjected to a mechanical stress.
Alperm is a class of alloys comprising 83-90% of iron and 10-17% of aluminium. The most widely used composition is with 16% Al.
A liquid metal is a metal or a metal alloy which is liquid at or near room temperature.
In Physics, antisymmetric exchange, also known as the Dzyaloshinskii–Moriya interaction (DMI), is a contribution to the total magnetic exchange interaction between two neighboring magnetic spins, and . Quantitatively, it is a term in the Hamiltonian which can be written as
High-entropy alloys (HEAs) are alloys that are formed by mixing equal or relatively large proportions of (usually) five or more elements. Prior to the synthesis of these substances, typical metal alloys comprised one or two major components with smaller amounts of other elements. For example, additional elements can be added to iron to improve its properties, thereby creating an iron-based alloy, but typically in fairly low proportions, such as the proportions of carbon, manganese, and others in various steels. Hence, high-entropy alloys are a novel class of materials. The term "high-entropy alloys" was coined by Taiwanese scientist Jien-Wei Yeh because the entropy increase of mixing is substantially higher when there is a larger number of elements in the mix, and their proportions are more nearly equal. Some alternative names, such as multi-component alloys, compositionally complex alloys and multi-principal-element alloys are also suggested by other researchers.
Brent Fultz is an American physicist and materials scientist and one of the world's leading authorities on statistical mechanics, diffraction, and phase transitions in materials. Fultz is the Barbara and Stanley Rawn Jr. Professor of Applied Physics and Materials Science at the California Institute of Technology. He is known for his research in materials physics and materials chemistry, and for establishing the importance of phonon entropy to the phase stability of materials. Additionally, Fultz oversaw the construction of the wide angular-range chopper spectrometer (ARCS) instrument at the Spallation Neutron Source and has made advances in phonon measuring techniques.
κ-Carbides are a special class of carbide structures. They are most known for appearing in steels containing manganese and aluminium where they have the molecular formula (Fe,Mn)
3AlC.
A silicide hydride is a mixed anion compound that contains silicide (Si4− or clusters) and hydride (H−) anions. The hydrogen is not bound to silicon in these compounds. These can be classed as interstitial hydrides, Hydrogenated zintl phases, or Zintl phase hydrides. In the related silanides, SiH3− anions or groups occur. Where hydrogen is bonded to the silicon, this is a case of anionic hydride, and where it is bonded to a more complex anion, it would be termed polyanionic hydride.
Terbium compounds are compounds formed by the lanthanide metal terbium (Tb). Terbium generally exhibits the +3 oxidation state in these compounds, such as in TbCl3, Tb(NO3)3 and Tb(CH3COO)3. Compounds with terbium in the +4 oxidation state are also known, such as TbO2 and BaTbF6. Terbium can also form compounds in the 0, +1 and +2 oxidation states.
The nucleon magnetic moments are the intrinsic magnetic dipole moments of the proton and neutron, symbols μp and μn. The nucleus of an atom comprises protons and neutrons, both nucleons that behave as small magnets. Their magnetic strengths are measured by their magnetic moments. The nucleons interact with normal matter through either the nuclear force or their magnetic moments, with the charged proton also interacting by the Coulomb force.