Variations in Magnetic Properties of SmCo5/Fe Exchange-Coupled Bilayers with Increasing Fe Thickness

Abstract

Exchange-coupled hard/soft magnetic materials have been widely studied during the last decade because of the prediction that these magnetic materials would have high energy-products. The soft and hard magnetic phases are exchange-coupled at particular grain sizes to give single-phase magnetic behavior. The grain size of the soft phase depends on the nature of the hard phase, and is usually around 10 nm. In this work, we studied soft phase exchange coupling with a hard phase at grain sizes of more than 10 nm to investigate the changes in magnetic properties, particularly the energy products, of nanocomposite hard/soft magnets. Bilayers of SmCo5/Fe were fabricated using magnetron sputtering on a 70-nm-Cr-buffered Si (100) substrate. The Fe thickness was varied up to 40 nm with 20 nm of SmCo5. Magnetic measurements were made using an alternating gradient magnetometer. In all the samples, the phases were strongly exchange-coupled with each other. The magnetization was found to increase and the coercivity to decrease with increasing Fe thickness. The energy product first increased and then decreased.