Dysprosium (pictured) is a rare earth helimagnet. A nanolayer of dysprosium has been included in a spin valve device constructed by scientists from the Russian Academy of Sciences.© Björn Wylezich / Alamy Stock Photo
A research team in Russia has developed a new method using a modified ‘spin valve’ to study the magnetic state of nanolayers of the rare-earth helimagnet, dysprosium1.The study, published in the journal of Physics of Metals and Metallography, will improve research on the interactions between electron spin, charge and magnetism that could advance the emerging technology of spintronics.
In addition to electrical charge, electrons have a property known as spin that is being explored as an alternative information carrier that could usher in a new generation of ultra-low power ‘spintronics’. The ordering of electron spins is what gives rise to magnetism, and the interaction between these three effects – charge, spin and magnetism – is at once complex, exotic, and potentially powerful in information processing terms.
Roman Zavornitsyn, and colleagues from the Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences have now modified a spin valve device by inserting a layer of helimagnetic dysprosium – a rare-earth that has unusual helical antiferromagnetic ordering at low temperatures.
“Characterizing the magnetic state of nanolayers of this helimagnet is challenging using conventional neutron scattering methods, given the small amount of rare-earth metal,” explains Zavornitsyn. “Using a spin valve device makes it possible to obtain quality information about the magnetic state of the helimagnet nanolayers without the need for big facilities.”
The spin valve included layers of an antiferromagnet (FeMn), a ferromagnetic alloy (CoFe), helimagnetic dysprosium, and nonmagnetic copper.
“The inclusion of a layer with a helicoidal magnetic structure in the spin valve affects the magnetization reversal of adjacent ferromagnetic layers,” says Zavornitsyn.
Magnetoresistance measurements showed that a change in the strength of the magnetic field and the direction of the magnetic moments of the ferromagnetic layers, which are coupled with the helimagnet, led to a change in the magnetoresistance of the spin valve.
The researchers also performed x-ray diffraction and reflectivity analyses, which showed that the dysprosium layer is polycrystalline and contains crystallites with a helicoid axis oriented perpendicular to the film plane. These measurements also revealed that the CoFe/Cu/CoFe nanostructure, in which spin-dependent electron scattering takes place, has perfect microstructure and smooth interfaces, which give rise to large magnetoresistance.
“Now we plan to use this method to study other types of helimagnets,” says Zavornitsyn. “A promising direction is the search for new spintronic effects in chiral magnetics arising from the interaction of spin and charge currents with a magnetic spiral.”