spinglass

A spinglass is a disordered magnetic state characterized by competing ferromagnetic and antiferromagnetic interactions between magnetic moments, called spins. This competition prevents the spins from settling into a simple, ordered arrangement like that found in ferromagnets or antiferromagnets. Instead, the spins freeze in a random, frustrated configuration below a certain temperature.

The term "spinglass" was coined by Samuel F. Edwards and P. W. Anderson. These materials exhibit properties that are unusual for magnets. For instance, their magnetic susceptibility shows a sharp peak at a characteristic temperature, known as the glass transition temperature, below which their magnetic behavior becomes history-dependent. This means the magnetization of a spinglass depends on whether it was cooled in a magnetic field or in zero field.

Spinglasses are typically formed from dilute alloys of magnetic atoms in a non-magnetic host metal, such as iron in gold. The interactions between the magnetic atoms are mediated by conduction electrons and are oscillatory, leading to both attractive (ferromagnetic) and repulsive (antiferromagnetic) forces depending on the distance between the magnetic atoms. The randomness in the positions of the magnetic atoms ensures a disordered mixture of these interactions.

The study of spinglasses has been significant in condensed matter physics due to their connection to concepts of disorder, frustration, and complex energy landscapes. They serve as a model system for understanding disordered systems in general, with applications extending to fields beyond magnetism, including neural networks and optimization problems. The existence of multiple low-energy states, or ground states, is a hallmark of spinglass behavior, making their study a rich area of theoretical and experimental research.