# Synopsis: Oxides Combine to Create Magnets

New research has identified a rare form of magnetism at the interface between two different oxide compounds.

Most of your garden-variety magnets are made with elements in the middle of the periodic table. However, physicists have recently found magnetic properties coming from unexpected elements, such as oxygen. In a new development, Riki Oja of Aalto University, Finland, and collaborators report in Physical Review Letters on the first observation of permanent magnetism at the interface between two nonmagnetic oxides.

The classic ferromagnet is an element like iron or cobalt, in which the $3d$ orbital is only partially filled with electrons. In certain situations, the spins of these $d$ electrons can align with each other to give the material an overall magnetic moment. Although less common, elements with unfilled $p$ orbitals, like oxygen, can exhibit a similar spin alignment. This “non-$d$” orbital arrangement is called ${d}^{0}$ ferromagnetism.

Previous work has found ${d}^{0}$ ferromagnetism in doped oxides and oxides with defects. The team decided to look at a different class of oxygen compounds, called perovskites. The unique cubic structure of these materials sometimes gives rise to interesting properties, including magnetoresistance and ferroelectricity. To generate ferromagnetism, the team investigated combinations of two normal perovskites: ${\text{SrTiO}}_{3}$ with either ${\text{KNbO}}_{3}$, ${\text{NaNbO}}_{3}$, or ${\text{KTaO}}_{3}$. In certain pairings, electrons on metal $d$ orbitals or electron holes on oxygen $p$ orbitals become confined to the two-dimensional interface between the oxides. The researchers showed with computer simulations that hole-type interfaces could generate a spin alignment of the electron holes. On the experimental side, for several of the oxide combinations the team observed ferromagnetic hysteresis loops at room temperature. The discovery could lead to new routes towards multiferroics. – Michael Schirber

### Announcements

More Announcements »

Metamaterials

## Next Synopsis

Materials Science

## Related Articles

Magnetism

### Focus: Supersensitive Needle Magnetometer

A tiny, needle-shaped ferromagnet could form a magnetic sensor far better than the current best instruments, according to theory.   Read More »

Quantum Information

### Synopsis: Even-Handed Control of Quantum Dot Qubits

A new way to control the coupling of spins between adjacent quantum dots produces qubits that are less susceptible to electronic noise. Read More »

Spintronics

### Synopsis: With Heat Comes Current

Researchers have observed spin-dependent thermoelectric currents in superconductors—a finding that could lead to precise cryogenic thermometers. Read More »