Press Release: New Form of Magnetic Order Discovered in the Element Neodymium

The element neodymium is an important component in strong magnets used in many applications, from mobile phones to wind turbines. Despite these areas of use, magnetism in pure neodymium has perplexed the scientific community in more than a half century. Researchers from Uppsala University and Radboud University in the Netherlands have now shown that neodymium shows a hitherto unknown form of magnetic order, built of a mixture of magnetic spirals.

The different spirals, called spin spirals, easily tangles into each other which means that there is not a well-defined ground state, but the magnetic structure is always changing slowly over time. The behaviour reminds largely of how the atoms in ordinary glass are not frozen in place but are constantly moving. This new type of dynamic magnetic order is therefore called a spin spiral glass. Besides from being able to describe neodymium’s magnetism, it is likely that the dynamics exhibited by the spin spiral glass also can be used to describe phenomena in completely different fields, for example artificial intelligence which mimics the behaviour of the brain.

“Neodymium’s magnetism has been debated over a long time. Our results also show that the well-studied behaviour of spin glass can occur also in materials which are not disordered, which one previously thought. This means that there are driving forces behind these phenomena which have not yet been fully understood and reasonably there should be many other materials than neodymium that behave like spin spiral glasses,” says Anders Bergman, researcher at the Department of Physics and Astronomy at Uppsala University.

“Now we have shown that the phenomenon spin spiral glass itself exists and have a basic understanding of its cause but we want to go further and understand even more about the driving forces behind this phenomenon so we plan to continue studying both neodymium but also other materials which we believe may show similar behaviour,” says Diana Iuşan, researcher at the Department of Physics and Astronomy at Uppsala University.

At Uppsala University, the researchers Anders Bergman, Diana Iuşan, Lars Nordström and Olle Eriksson have worked on the study.

More About Magnetic Order

Simplified, one may describe a magnetic material like there are small rod magnets on each atom. These small atomic magnets are generated by the electrons in the material which have a quantum mechanical property called “spin”. Depending on how the atomic magnets arrange themselves one may divide magnetic materials into different varieties. If all atomic magnets point in the same direction, the material behaves like one large magnet and has a magnetic order called ferromagnetism (after the name of iron, ferrum in Latin). If the atomic magnets point in completely random directions one instead gets a paramagnet. If the atomic magnets arrange themselves like a spiral, i.e. an ordered structure where the magnets turn around some axis, the magnetic order is called a spin spiral.

Spin glass is a class of magnetic materials which at a first glance seems to be an unordered paramagnet but which yet shows dynamics, i.e. motions, which follow certain patterns over time. The dynamics which spin glasses show can also be seen on completely different phenomena which do not have anything with magnetism to do, e.g. in biological systems. Spin spiral glass may be seen as a variety of spin glass, with similar dynamics, but where the magnetism consists of a mixture of various spin spirals and therefore are not as unordered as an ordinary spin glass.

More About the Element Neodymium

Neodymium is an element belonging to the rare earth elements. These elements are not always as rare as the name sounds but they have historically been hard to extract. Neodymium is foremost used as a component in the strong permanent magnet Nd₂Fe₁₄B which is an important component in many different applications, from magnetic hard drives to electric engines. The magnetic order in neodymium has previously been studied foremost with neutron scattering so hopefully, the new results on neodymium’s magnetic order might in the future be complemented with studies at the advanced neutron source ESS which is under construction in Lund.

Contact

Anders Bergman, 070-4250588, anders.bergman@physics.uu.se

Article reference

Self-induced spin glass state in elemental and crystalline neodymium, Science, DOI: 10.1126/science.aay6757

Linda Koffmar
Translation: Johan Wall