Search results for "MAGNETORESISTANCE"
showing 10 items of 173 documents
SAMs Based Device Fabrication and Characterization
2015
Despite the high potentiality of SAMs for spintronics, not many results exist at the moment in the literature. This lack of results is mainly due to the difficulty to fabricate the devices. The two main technological problems consist in the ferromagnetic electrodes compatibility issues with wet chemistry and the short-circuit formation during top electrode deposition. A part of this thesis has been committed to overcome these technological problems. This chapter will explain the steps that led us to the development of SAMs-based magnetic tunnel nanojunctions.
Probing the electronic states of high-TMR off-stoichiometric Co2MnSi thin films by hard x-ray photoelectron spectroscopy
2014
The tunnel magnetoresistance ratio (TMR) of fully epitaxial magnetic tunnel junctions with an off-stoichiometric Co${}_{2}$MnSi Heusler alloy has been shown to exhibit a systematic dependence on Mn content, reaching 1135% at 4.2 K for Co${}_{2}$Mn${}_{1.29}$Si. In this paper, we explain the behavior of the observed TMR ratio using ab initio calculations and hard x-ray photoelectron spectroscopy (HAXPES). For the Mn-deficient samples, we show that the the drop of the TMR is caused by Co antisite atoms, which impose extra states into the minority-spin band gap. On the other hand, Mn-excess composition shows nearly half-metallic behavior. This result can be intuitively understood since both Co…
Introduction to Self-Assembled Monolayers
2015
One of the most exciting targets of molecular spintronics field is to go towards multifunctional devices where the properties can be accurately controlled and actively changed. Spin dependent hybridization at the metal/molecule interface could thus be used in the tailoring of the resistive and magnetoresistive response of spintronic devices exploiting chemistry versatility. In this new direction, Self-Assembled Monolayers (SAMs) appear as highly promising candidates since each part and function of this system can be modulated independently (like a molecular LEGO building unit). Despite highly promising, they are still scarcely investigated in the literature probably due to the difficulties …
Spin-resolved low-energy and hard x-ray photoelectron spectroscopy of off-stoichiometric Co2MnSi Heusler thin films exhibiting a record TMR
2015
Half-metallic Co2MnSi-based Heusler compounds have attracted attention because they yield very high tunnelling magnetoresistance (TMR) ratios. Record TMR ratios of 1995% (at 4.2 K) are obtained from off-stoichiometric Co2MnSi-based magnetic tunnel junctions. This work reports on a combination of band structure calculations and spin-resolved and photon-polarisation-dependent photoelectron spectroscopy for off-stoichiometric Heusler thin films with the composition Co2Mn1.30Si0.84. Co and Mn are probed by magnetic dichroism in angle-resolved photoelectron spectroscopy at the 2p core level. In contrast to the delocalised Co 3d states, a pronounced localisation of the Mn 3d states is deduced fro…
Total ionizing dose (TID) evaluation of magnetic tunnel junction (MTJ) current sensors
2015
Abstract The paper shows an experimental study to know the behaviour of tunnel magnetoresistive effect-based current sensors configured in a Wheatstone bridge in response to irradiation. In particular the sensitivity, hysteresis, output offset voltage and input resistance are discussed when the sensors are submitted to a total irradiation dose of 43 krad with 36 krad/h dose rate. The same electrical parameters were studied subsequently once the irradiated sensors were submitted to an 80 °C annealing process. The studied TMR sensors are applied in a switched-mode power converter for space application.
Electrical Characterization of a Magnetic Tunnel Junction Current Sensor for Industrial Applications
2012
The objective of the work was the design of a Wheatstone bridge current sensor using MTJ as magnetoresistive elements. Each one of the four resistances of the bridge consists on 360 MTJ single elements connected in series for improved electrical robustness. A printed circuit board (PCB) was designed with a U-shaped copper trace placed under the PCB maintaining a 1.1 mm separation distance between sensor and trace. A 160% of tunnel magnetoresistance effect in the single junction and a 120% in its corresponding series elements connection has been achieved with a sensitivity of 9.2 Ω/Oe in a 65 Oe linear range. The DC sensor sensitivity in response to an external DC current sweeps of ±10, ±20,…
GMR Based Sensors for IC Current Monitoring
2013
The Giant MagnetoResistance (GMR) effect is a magnetic coupling mechanism that can be obtained in multilayer structures of few nanometers thick. In these devices, and at room temperature, the resistance is a function of the external magnetic field, at optimal levels for being used as sensors. Since the GMR effect was reported, scientists and engineers have dedicated their effort to this topic. This way, after two decades, a a very good knowledge of the GMR underlying physics together with notable designs of GMR based devices are nowadays available. They were initially used in the read heads of hard drives, but the constant evolution that this technology has experienced has open new fields o…
Magneto-Transport Results in SAM Based MTJs
2015
This chapter is dedicated to the description of the magneto-transport results obtained in LSMO/SAM/Co magnetic tunnel nanojunctions fabricated by nanoindentation lithography technique. We started by focusing on the study of LSMO/C12P/Co MTJs. This because C12P is a medium size alkyl chain: long enough to avoid short-circuits in the junction but short enough to give a device resistance in the order of few tens of MO and thus easier to measure. Next, we started to tune the molecule thickness from C10P to C18P (from 10 carbon atoms in the alkyl chain to 18). This allowed on one hand to validate our system by comparing the exponential increase of the junction resistance to the one reported in t…
Magneto-Transport Results in Alq3 Based OSVs
2015
The achievement of good magnetoresistance signal at room temperature is an important requirement for the possible future development of organic devices for applications. However, until now only few works reported room temperature MR effect in organic spin valves (OSVs). In this regard, this chapter is dedicated to the investigation of Alq3-based OSVs where Alq3 molecule was chosen since it is a standard material in the field. A systematic study on Co/Alq3/Co OSVs will be presented showing room temperature MR results. Moreover, inelastic electron tunneling spectroscopy (IETS) technique will be used to prove spin injection into the organic layer. Finally, an insulating oxide barrier (Al2O3 or…