Thermal Annealing of Ferromagnetic/Antiferromagnetic Materials

Magnetic materials are used extensively in the manufacturing of computing device memory. In this project we investigate crystalline thin films composed of layered ferromagnetic (FM) and antiferromagnetic (AFM) materials with the goal of developing next generation computer memory storage. In particular, we have designed a thermal annealer that allows for exposing these magnetic samples to an applied magnetic field while in a vacuum environment. This procedure is important because it establishes an exchange bias in the magnetic thin film material. After the thin films are grown and characterized in the laboratory, they are loaded in the annealer and the pressure is lowered to ~100 mTorr. Next, the samples are heated through the magnetic ordering temperature of the AFM (Neel Temperature), but below the magnetic ordering temperature of the FM (Curie Temperature) so that TN<T<TC. When T>TN the magnetic moments of the AFM are in disarray. At this point we apply an external magnetic field, B= .5 T, while allowing the samples to cool down. When T<TN, the interface of the FM-AFM become permanently aligned with the externally applied magnetic field. This anisotropy at the FM-AFM interface is responsible for the phenomena know as exchange bias. Understanding this interface, as well as exchange bias is crucial in developing the materials and devices that will power future generation electronic devices.