Theory explains ferromagnetic superconductor behavior

phys.org | 10/12/2018 | Staff
Cayley1561 (Posted by) Level 3
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Researchers from France and Russia have offered a theoretical explanation for the behavior of a recently discovered material combining superconducting and ferromagnetic properties. The new theoretical model also predicts so far unobserved effects in materials of this kind. The study was published in Physical Review Letters.

Ferromagnetism and superconductivity are, in a way, two opposed tendencies that seemingly cannot coexist in one crystal. Indeed, a superconductor accommodates an electric current with zero resistance. When placed in a magnetic field, such a material expels that field from its bulk in what is known as the Meissner effect. By contrast, a ferromagnet is magnetized and thus carries a magnetic field in its bulk. It would appear, therefore, that a material cannot simultaneously exhibit superconductivity and ferromagnetism.

Compounds - Focus - Research - Attention - Observations

However, europium-based compounds have recently emerged as the focus of research attention, when observations showed they could simultaneously exhibit ferromagnetism and superconductivity. Besides its importance for fundamental science, the coexistence of these two phenomena in one material offers intriguing possibilities for device design. It holds the promise of superconducting spintronics, that is, devices working with information encoded by spins, with no dissipation.

An ordinary fridge magnet is an example of a ferromagnet whose so-called Curie point lies above room temperature. Below that critical temperature, a ferromagnetic material is magnetized due to the parallel alignment of the intrinsic magnetic momenta, or spins, of outer-shell electrons. It may seem counterintuitive, but down at the microscopic scale, the nature of this spontaneous ordering is electrical rather than magnetic: The Coulomb interaction energy of the electrons in a ferromagnet is lower for the parallel spin configuration. As a result, each spin may be thought of as residing in an average, or exchange, field generated by the other spins.

Mechanisms - Interaction - Electrons - Moments

There are two mechanisms mediating the interaction of superconducting electrons and magnetic moments. Namely, the electromagnetic...
(Excerpt) Read more at: phys.org
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