Magnetoresistance

About: Magnetoresistance is a research topic. Over the lifetime, 30611 publications have been published within this topic receiving 590345 citations.

Large, non-saturating magnetoresistance in WTe2.

Abstract: The magnetoresistance effect in WTe2, a layered semimetal, is extremely large: the electrical resistance can be changed by more than 13 million per cent at very high magnetic fields and low temperatures. Apply a magnetic field to a magnetoresistive material and its electrical resistance changes — a technologically useful phenomenon that is harnessed, for example, in the data-reading sensors of hard drives. Mazhar Ali and colleagues have now identified a material (tungsten ditelluride or WTe2) in which the magnetoresistance effect is unusually large: the electrical resistance can be changed by more than 13 million per cent. Its remarkable magnetoresitance is evident at very high magnetic fields and at extremely low temperatures, so practical applications are not yet in prospect. But this finding suggests new directions in the study of magnetoresistivity that could ultimately lead to new uses of this effect. Magnetoresistance is the change in a material’s electrical resistance in response to an applied magnetic field. Materials with large magnetoresistance have found use as magnetic sensors1, in magnetic memory2, and in hard drives3 at room temperature, and their rarity has motivated many fundamental studies in materials physics at low temperatures4. Here we report the observation of an extremely large positive magnetoresistance at low temperatures in the non-magnetic layered transition-metal dichalcogenide WTe2: 452,700 per cent at 4.5 kelvins in a magnetic field of 14.7 teslas, and 13 million per cent at 0.53 kelvins in a magnetic field of 60 teslas. In contrast with other materials, there is no saturation of the magnetoresistance value even at very high applied fields. Determination of the origin and consequences of this effect, and the fabrication of thin films, nanostructures and devices based on the extremely large positive magnetoresistance of WTe2, will represent a significant new direction in the study of magnetoresistivity.

Theory of the perpendicular magnetoresistance in magnetic multilayers.

Abstract: In the talk presented by one of us (AF) at Cargese, the mechanisms of the giant magnetoresistance (MR) in magnetic multilayers were discussed very generally for both the CIP (current in plane) and CPP (current perpendicular to the planes) geometries. A so general discussion would be too long for these proceedings and the present paper will be restricted to the CPP case. We present the theoretical model that we have recently worked out [1,2] and discuss its application to experimental data obtained for the Ag/Co and Cu/Co systems at Michigan State University [3,4,5] and presented at Cargese by Pr. P.A. Schroeder [6]. We describe the specific fundamental problems related to the spin accumulation effects occuring in the CPP geometry and we calculate the magnetoresistance. The expressions of the MR become relatively simple in the limit where the layer thicknesses are much smaller than the spin diffusion length and we justify the analysis of experimental results developed at Michigan State University [3–6]. We also relate our theory to those of Johnson et al [7,8], van Son et al [9] and Zhang and Levy [10]. Of course, it is not in the scope of the present paper to develop calculations presented elsewhere in detail [1] and we will focus on the presentation of the basis of the model and the discussion of our results.

Magnetic effects at the interface between non-magnetic oxides

Abstract: The electronic reconstruction at the interface between two insulating oxides can give rise to a highly conductive interface. Here we show how, in analogy to this remarkable interfaceinduced conductivity, magnetism can be induced at the interface between the otherwise non-magnetic insulating perovskites SrTiO3 and LaAlO3. A large negative magnetoresistance of the interface is found, together with a logarithmic temperature dependence of the sheet resistance.At lowtemperatures, the sheet resistance reveals magnetic hysteresis.Magnetic ordering is a key issue in solid-state science and its underlying mechanisms are still the subject of intense research. In particular, the interplay between localized magnetic moments and the spin of itinerant conduction electrons in a solid gives rise to intriguingmany-body effects such as Ruderman–Kittel–Kasuya–Yosida interactions3, the Kondo effect4 and carrier-induced ferromagnetism in diluted magnetic semiconductors5. The conducting oxide interface now provides a versatile system to induce and manipulate magnetic moments in otherwise non-magnetic materials.

Giant magnetoresistance in organic spin-valves

Abstract: A spin valve is a layered structure of magnetic and non-magnetic (spacer) materials whose electrical resistance depends on the spin state of electrons passing through the device and so can be controlled by an external magnetic field. The discoveries of giant magnetoresistance and tunnelling magnetoresistance in metallic spin valves have revolutionized applications such as magnetic recording and memory, and launched the new field of spin electronics--'spintronics'. Intense research efforts are now devoted to extending these spin-dependent effects to semiconductor materials. But while there have been noteworthy advances in spin injection and detection using inorganic semiconductors, spin-valve devices with semiconducting spacers have not yet been demonstrated. pi-conjugated organic semiconductors may offer a promising alternative approach to semiconductor spintronics, by virtue of their relatively strong electron-phonon coupling and large spin coherence. Here we report the injection, transport and detection of spin-polarized carriers using an organic semiconductor as the spacer layer in a spin-valve structure, yielding low-temperature giant magnetoresistance effects as large as 40 per cent.

Current-Induced Switching of Domains in Magnetic Multilayer Devices

Abstract: Current-induced switching in the orientation of magnetic moments is observed in cobalt/copper/cobalt sandwich structures, for currents flowing perpendicularly through the layers. Magnetic domains in adjacent cobalt layers can be manipulated controllably between stable parallel and antiparallel configurations by applying current pulses of the appropriate sign. The observations are in accord with predictions that a spin-polarized current exerts a torque at the interface between a magnetic and nonmagnetic metal, due to local exchange interactions between conduction electrons and the magnetic moments.