Ferromagnetic materials, such as cobalt, play a large role in modern electronic storage devices and the downsizing of such devices brings about new problems. As such, a device was designed and fabricated to test the electrical and thermal properties of a thin cobalt film on two substrates: hexagonal boron nitride and silicon dioxide. Gold contacts placed on the channel allowed the resistivity of this channel on silicon dioxide to be measured to be (26.75 ± 0.27Random ± 0.71systematic)μΩm which is consistent with other films of this nature on similar substrates. Anisotropic magnetoresistance in the channel was also found to be consistent with literature. A fabricated gold heater was used to create a thermal gradient along the channel and as such, the thermopower was measured to be (-16.7 ± 3.3Random ± 2.1systematic)μV/K on the SiO2 which is similar to that reported by Avery et al for a similar cobalt film. The variation of this thermopower with magnetisation direction of the film was too consistent with literature. Unfortunately, no measurements on the hBN substrate could be made due to mistakes in the fabrication process but this leaves room for further study next semester after repairing the device. A test of the thermal profile along the channel revealed that the temperature gradient is largely unaffected by the direction of the magnetisation of the channel.
BenSnow6/Semester-1-MPhys-Report
Magnetothermoelectric effects in thin cobalt films on hexagonal boron nitride for graphene spintronics applications