physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...

, amorphous magnet refers to a

magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...

made from

amorphous solid In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid) is a solid that lacks the long-range order that is a characteristic of a crystal. The terms "glass" and "glassy solid" are sometimes used synonymousl ...

s. Below a certain temperature, these magnets present permanent

magnetic Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other. Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, m ...

phases produced by randomly located

magnetic moment In electromagnetism, the magnetic moment or magnetic dipole moment is the combination of strength and orientation of a magnet or other object or system that exerts a magnetic field. The magnetic dipole moment of an object determines the magnitude ...

s. Three common types of amorphous magnetic phases are asperomagnetism, speromagnetism and sperimagnetism, which correspond to

ferromagnetism Ferromagnetism is a property of certain materials (such as iron) that results in a significant, observable magnetic permeability, and in many cases, a significant magnetic coercivity, allowing the material to form a permanent magnet. Ferromagne ...

antiferromagnetism In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions. ...

and

ferrimagnetism A ferrimagnetic material is a material that has populations of atoms with opposing magnetic moments, as in antiferromagnetism, but these moments are unequal in magnitude, so a spontaneous magnetization remains. This can for example occur wh ...

, respectively, of crystalline solids.

Spin glass In condensed matter physics, a spin glass is a magnetic state characterized by randomness, besides cooperative behavior in freezing of spins at a temperature called the "freezing temperature," ''T''f. In ferromagnetic solids, component atoms' ...

models can present these amorphous types of magnetism. Due to random

frustration In psychology, frustration is a common emotional response to opposition, related to anger, annoyance and disappointment. Frustration arises from the perceived resistance to the fulfillment of an individual's Will (philosophy), will or goal and ...

, amorphous magnets possess many nearly degenerate

ground state The ground state of a quantum-mechanical system is its stationary state of lowest energy; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state ...

s. The terms for the amorphous magnetic phases were coined by

Michael Coey John Michael David Coey (born 24 February 1945), known as Michael Coey, is a Belfast-born experimental physicist working in the fields of magnetism and spintronics. He is an Emeritus professor at the Trinity College Dublin (TCD). Life Ed ...

in 1970s. The Greek root ''spero/speri'' () means 'to scatter'.

Phases

Single species

Asperomagnetism

Asperomagnetism is the equivalent of

for a disordered system with random magnetic moments. It is defined by short range correlations of locked magnetic moments within small noncrystalline regions, with average long range correlations. Speromagnets possess a permanent net magnetic moment. An example of an asperomagnets is amorphous YFe₃ and DyNi₃.

Speromagnetism

Speromagnetism is the equivalent of

for a disordered system with random magnetic moments. It is defined by short range correlations of locked magnetic moments within small noncrystalline regions, without average long range correlations. Speromagnets do not have a net magnetic moment. An example of a solid presenting speromagnetism is amorphous YFe₂ and can be detected using

Mössbauer spectroscopy Mössbauer spectroscopy is a spectroscopic technique based on the Mössbauer effect. This effect, discovered by Rudolf Mössbauer (sometimes written "Moessbauer", German: "Mößbauer") in 1958, consists of the nearly recoil-free emission and a ...

Multiple species

Sperimagnetism

Sperimagnetism is the equivalent of

for a disordered system with two or more species of magnetic moments, with at least one species locked in random magnetic moments. Sperimagnets possess a permanent net magnetic moment. When all species are the same, this phase is equivalent to asperomagnetism.

Notes

References

{{Magnetic states Quantum phases Magnetic ordering Amorphous solids