title: Magnetic tunnel junctions with integrated thermometers for magnetothermopower measurements.
abstract: Magnetic tunnel junction (MTJ) micropillars were fabricated with integrated thermometers and a heater line (HL) for thermovoltage measurements. This novel thermometer configuration enabled a direct measurement of ΔT across the MTJ micropillar. The MTJ devices were patterned from a CoFeB/MgO/CoFeB stack, with a 1.2 nm to 1.6 nm MgO wedge across the wafer, resulting in resistance area products in the range of 0.7 kΩ · µm2<  R  ×  A  <  55 kΩ · µm2. This allowed the measurement of thermoelectric properties as a function of the tunnel barrier thickness. The thermometers showed a homogeneous heating behavior for all devices across the wafer. Combining the in-stack temperature measurements and finite element simulations the thermal profile across the MTJ structure and the thermopower were estimated with a noticeable improvement of the measurement accuracy. The studied MTJ structures showed tunneling magnetoresistance (TMR) ratios up to 125%, and tunneling magnetothermopower (TMTP) up to 35%.
authors.affiliation: INL-International Iberian Nanotechnology Laboratory, Av. Mestre José Veiga s/n, Braga 4715-330, Portugal.
authors.forename: T
authors.initials: T
authors.lastname: Böhnert
authors.forename: S
authors.initials: S
authors.lastname: Serrano-Guisan
authors.forename: E
authors.initials: E
authors.lastname: Paz
authors.forename: B
authors.initials: B
authors.lastname: Lacoste
authors.forename: R
authors.initials: R
authors.lastname: Ferreira
authors.forename: P P
authors.initials: PP
authors.lastname: Freitas