Colloquium: Dr. Imre Bakonyi
Location
Physics : 401
Date & Time
October 21, 2015, 3:30 pm – 4:30 pm
Description
TITLE: Giant magnetoresistance (GMR) in magnetic nanostructures: discovery, physical mechanism and impact on data storage
ABSTRACT: In nanoscale layered structures in which ferromagnetic (FM) and non-magnetic (NM) metals alternate with individual layer thicknesses smaller than the electron mean-free path of the corresponding bulk metals, new physical phenomena may arise. A striking example is the GMR effect, an unprecedentedly large change of resistance in magnetic field, which was discovered in 1988. The GMR effect have found important application in read heads of hard disk drives.
In the present talk, a description of spin-dependent scattering processes occurring in various magnetic nanostructures will be described, together with an explanation of the physical mechanism underlying the GMR phenomenon. A general overview of spin-dependent transport processes in ideal magnetic nanostructures will be given. The two limiting cases are (i) perfect nanoscale metallic multilayers in which FM layers are separated by NM layers and (ii) classical granular metals in which nanoscale non-interacting ferromagnetic regions with superparamagnetic (SPM) characteristics are embedded in a NM matrix. However, real magnetic nanostructures are often somewhere between the two ideal cases as will be demonstrated by discussing our results on the GMR in electrodeposited multilayer films [1]. The talk intends to give a unified view of GMR for both layered and granular magnetic nanostructures, either ideal or non-ideal.
1. I. Bakonyi, L. Péter: Electrodeposited multilayer films with giant magnetoresistance (GMR): progress and problems. Progr. Mater. Sci. 55, 107-245 (2010)
ABSTRACT: In nanoscale layered structures in which ferromagnetic (FM) and non-magnetic (NM) metals alternate with individual layer thicknesses smaller than the electron mean-free path of the corresponding bulk metals, new physical phenomena may arise. A striking example is the GMR effect, an unprecedentedly large change of resistance in magnetic field, which was discovered in 1988. The GMR effect have found important application in read heads of hard disk drives.
In the present talk, a description of spin-dependent scattering processes occurring in various magnetic nanostructures will be described, together with an explanation of the physical mechanism underlying the GMR phenomenon. A general overview of spin-dependent transport processes in ideal magnetic nanostructures will be given. The two limiting cases are (i) perfect nanoscale metallic multilayers in which FM layers are separated by NM layers and (ii) classical granular metals in which nanoscale non-interacting ferromagnetic regions with superparamagnetic (SPM) characteristics are embedded in a NM matrix. However, real magnetic nanostructures are often somewhere between the two ideal cases as will be demonstrated by discussing our results on the GMR in electrodeposited multilayer films [1]. The talk intends to give a unified view of GMR for both layered and granular magnetic nanostructures, either ideal or non-ideal.
1. I. Bakonyi, L. Péter: Electrodeposited multilayer films with giant magnetoresistance (GMR): progress and problems. Progr. Mater. Sci. 55, 107-245 (2010)