Thermoelectric effects in magnetic nanostructures and the so-called spin caloritronics are attracting much interests. 1−11,27,28 Indeed it provides a new way to control and manipulate spin currents which are key elements of spin-based electronics.12,13 Here we report on the giant magnetothermoelectric effect in a magnetic tunnel junction. The thermovoltage in this geometry can reach 1 mV. Moreover a magneto-thermovoltage effect could be measured with ratio similar to the tunnel magnetoresistance ratio. The Seebeck coefficient can then be tuned by changing the relative magnetization orientation of the two magnetic layers in the tunnel junction. Therefore our experiments extend the range of spintronic devices application to thermoelectricity and provide a crucial piece of information for understanding the physics of thermal spin transport.Thermoelectricity has been known since 1821 with T.J. Seebeck. On one hand, the relation between the thermal and the electrical transport is an essential topic for both fundamental physics and for the future of energy-saving technologies.14,15 On the other hand the discovery of the giant magnetoresistance effect (GMR) and the tunnel magnetoresistance effect (TMR) enhanced the interest of the community for spin-dependent conductivity and gave rise to spintronics and multiple applications.12,13 Its interplay with thermal conductivity was introduced to describe the conventional Seebeck effect in ferromagnetic metals. 1−9,16−20 . The magnetothermoelectric effect has then be studied in magnetic systems such as magnetic multilayers and spin valves. 16−20 Moreover the thermoelectric effect has also been observed in non magnetic tunneling devices such as superconductorinsulator-normal metal (or superconductor) tunnel junctions. 21,22 Recently, thermal spin tunnelling effect from ferromagnet to silicon has been reported. Fig. 1a. To generate a temperature difference between the reference layer and the free layer, one electrode lead was heated using the laser beam from a laser diode with a wavelength of 780 nm and a tunable power from 0 to 125 mW. The temperature difference between both sides of the Al 2 O 3 barrier is defined as ∆T whereas the voltage difference is ∆V. In the linear response approximation, the total electric current I in the presence of ∆V and ∆T can be written as 7,16 (1) where G V is the electrical conductance, and G T is the thermoelectric coefficient related to the charge current response to the heat flux.The thermovoltage ∆V can be measured in an opencircuit geometry where I = 0, as shown in Fig. 1b. Considering equation (1) it leads to ∆V = − (G T /G V ) ∆T = − S ∆T, where S = G T /G V is the thermopower (TP) or Seebeck coefficient. ∆V was measured with a nanovoltmeter at room temperature (RT) with a magnetic field H applied along the in-plane easy axis of the free layer. The thermotunnel current was measured by a source-meter connecting the MTJ without any applied voltage, i.e. a closed-circuit, as shown in Fig. 1c. In the closed-circuit geome...

A magnetic tunnel junction sensor is proposed, with both the detection and the reference layers pinned by IrMn. Using the differences in the blocking temperatures of the IrMn films with different thicknesses, crossed anisotropies can be induced between the detection and the reference electrodes. The pinning of the sensing electrode ensures a linear and reversible output.It also allows tuning both the sensitivity and the linear range of the sensor. The authors show that the sensitivity varies linearly with the ferromagnetic thickness of the detection electrode. It is demonstrated that an increased thickness leads to a rise of sensitivity and a reduction of the operating range.