LAUSR

Magnetic anisotropy is a fundamental key parameter of magnetic materials that determines their applications. For ferromagnetic materials, the magnetic anisotropy can be easily detected by using conventional magnetic characterization techniques. However, due to the magnetic compensated structure in antiferromagnetic materials, synchrotron measurements, such as X-ray magnetic linear dichroism, are often needed to probe their magnetic properties. In this work, we observed an imprinted fourfold magnetic anisotropy in the amorphous ferromagnetic layer of FeRh/CoFeB heterostructures. The MOKE and ferromagnetic resonance measurements show that the easy magnetization axes of the CoFeB layer are along the FeRh〈110〉 and FeRh〈100〉 directions for the epitaxially grown FeRh layer in the antiferromagnetic and ferromagnetic states, respectively. The combined Monte Carlo simulation and first-principles calculation indicate that the fourfold magnetic anisotropy of the amorphous CoFeB layer is imprinted due to the interfacial exchange coupling between the CoFeB and FeRh moments from the magnetocrystalline anisotropy of the epitaxial FeRh layer. This observation of imprinting the magnetocrystalline anisotropy of antiferromagnetic materials on easily detected ferromagnetic materials may be applied to probe the magnetic structures of antiferromagnetic materials without using synchrotron methods. Capturing magnetic structural information using nanoscale thin films can make it easier to spot materials that exploit the spin properties of electrons for use in spintronics devices. Most magnets have their electron spins aligned in one direction, but antiferromagnets have alternating up/down spins that are useful for sensors. Qingfeng Zhan from East China Normal University in Shanghai and Run-Wei Li at the Chinese Academy of Sciences in Ningbo and colleagues now report a method that identifies antiferromagnets without the use of high-powered X-ray equipment. The team demonstrated that alloys with amorphous crystal structures can convert into ordered frameworks with distinct spin patterns after being thinly coated onto an antiferromagnet’s surface. Using a combination of magnetometermicroscopy and computer simulations, the researchers showed that the antiferromagnet imprinted its magnetic ordering onto the alloy through quantum mechanical coupling effects. An imprinted four-fold magnetic anisotropy was observed in the amorphous ferromagnetic layer of FeRh/CoFeB heterostructures. The easy magnetization axes of the CoFeB layer are along the FeRh〈110〉 and FeRh〈100〉 directions for the epitaxially grown FeRh layer in the antiferromagnetic and ferromagnetic states, respectively. The fourfold magnetic anisotropy of the amorphous CoFeB layer is imprinted due to the interfacial exchange coupling between the CoFeB and FeRh moments from the magnetocrystalline anisotropy of the epitaxial FeRh layer, which may be applied to probe the magnetic structures of antiferromagnetic materials without using synchrotron methods.