Synopsis: Anisotropy Defying Crystal Symmetry

Microscopic distribution of alloy constituents explains the puzzling magnetic anisotropy in (Ga,Mn)As films.
Synopsis figure
M. Birowska et al., Phys. Rev. Lett. (2012)

Much can be understood about the properties of a material just by analyzing the symmetry of its crystal structure with the tools of group theory. The conclusions of such an analysis for a given bulk material are often assumed to hold for its alloys too, but it is unclear if this is true when the distribution of added alloy constituents is not strictly random. An example is the dilute magnetic semiconductor (Ga,Mn)As, which exhibits in-plane magnetocrystalline anisotropy, even though the GaAs lattice symmetry does not allow it.

In Physical Review Letters, Magdalena Birowska at the University of Warsaw, Poland, and colleagues report calculations showing that a nonrandom distribution of magnetic ions in the dilute magnetic semiconductor (Ga,Mn)As can in fact explain the observed anisotropy. With the help of quantitative predictions from ab initio calculations and symmetry analysis they show that the puzzling anisotropy is caused by the preferred formation of manganese dimers along a specific crystalline direction at the growth surface. This work suggests that magnetic anisotropy could be controlled by varying the layer-by-layer growth of the material. In more general terms, the authors have shown how a specific microscopic distribution of constituents may affect the symmetry properties and macroscopic behavior of alloys in ways that go beyond the standard group theory analysis. – Athanasios Chantis


Announcements

More Announcements »

Subject Areas

SpintronicsMaterials Science

Previous Synopsis

Atomic and Molecular Physics

The Gravitational Aharonov-Bohm Effect

Read More »

Next Synopsis

Related Articles

Viewpoint: Electrical Signal Picks Up a Magnet’s Heartbeat
Magnetism

Viewpoint: Electrical Signal Picks Up a Magnet’s Heartbeat

Excitations in a magnet coupled to a microwave cavity can be detected electrically, providing a new way to study magnets in the quantum regime. Read More »

Focus: Crack Patterns Resemble Fluid Turbulence
Materials Science

Focus: Crack Patterns Resemble Fluid Turbulence

A statistical analysis of crack surfaces from three different materials reveals a deep connection with fluid turbulence and a potentially new approach to studying failed machine parts. Read More »

Viewpoint: A Boost for Superconducting Logic
Superconductivity

Viewpoint: A Boost for Superconducting Logic

A new choice of materials leads to more practically useful superconducting spin valves. Read More »

More Articles