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Abstract: Recently, highly sensitive strain gauges were developed, which are based on tunnel magnetoresistance (TMR) or giant magnetoresistance (GMR) effects combined with the inverse magnetostriction. GMR and TMR structures generally possess a symmetrical characteristic, which reflects the switching fields of the soft and hard layers, respectively. This characteristic can be changed by a stress field if the soft layer is replaced by a suitable magnetostrictive layer leading to a stress-induced rotation of the magnetostrictive layer with respect to the reference layer. Alternatively, both magnetic layers can be soft magnetic, one being positive and the other negative magnetostrictive. In this case, a stress applied on the stack leads to a reverse rotation of both layers due to the different sign in magnetostriction. This new approach is especially attractive since no reference layer is required which allows multilayering for GMR effect enhancement. This paper presents the stress biased characteristics of (FeCo/Cu/Ni) GMR trilayers in which the positive magnetostrictive FeCo and the negative magnetostrictive Ni replace the sensing and reference layer of a conventional GMR stack. The results can be interpreted by a simple model taking into account the magnetization direction of the individual layers and their response to mechanical strain in the range of 0.1–1‰. [Copyright &y& Elsevier]

This paper investigates the switching behavior of magnetostrictive micro-dot arrays by mechanical strain. These amorphous FeCoBSI micro-dot arrays with diameters of 1-5 μm and a thickness of 20 nm have been prepared on MEMS fabricated membrane structures. Magnetic force microscopy (MFM) has been used to obtain a spatially resolved switching behavior of these dots at different level of mechanical strain. For 20-nm-thick FeCoBSi dots, we have observed a strain induced switching starting at a level of about 0.04% of strain. In addition, finite-element simulations have been performed in order to correlate the MFM results with the local strain distribution of the membrane structure. [ABSTRACT FROM AUTHOR]

Abstract: Magnetostrictive tunneling magnetoresistive (TMR) pressure sensors have been developed by combining micro electrical–mechanical systems (MEMS) fabrication techniques with magnetic thin film technology. The sensing TMR elements with magnetostrictive Fe50Co50 free layers were placed on different positions on a 2-μm-thick Si membrane structure allowing localized strain measurements. Compressive or tensile mechanical strain up to 0.12% can be introduced by applying different air pressure (0.1–4bar) to the sealed membrane cavity, which in turn leads to a change in the magnetization direction due to the inverse magnetostrictive effect. For the first time, the strain-induced switching of the free layers has been characterized by means of magneto-optical Kerr effect (MOKE) measurements. [Copyright &y& Elsevier]