Volume 85, Issue 8, 15 April 1999
Index of content:
- GMR: FUNDAMENTALS II
Test of unified picture of spin-dependent transport in perpendicular (CPP) giant magnetoresistance and bulk alloys85(1999); http://dx.doi.org/10.1063/1.370402View Description Hide Description
Measurements of current perpendicular (CPP) magnetoresistance(MR) on hybrid and exchange-biased spin valves allow determination of the layer anisotropy parameter β for ferromagnetic alloys, thus allowing testing of whether this CPP β is similar to values obtained from direct measurements on, and theoretical estimates for, dilute bulk ferromagnetic alloys. Of special interest are alloys where β is expected to be negative. In this article, we derive a value of β for a alloy using such spin valves based upon permalloy. We confirm prior CPP-MR results that this β is negative, but our inferred value, is closer to bulk and theoretical estimates. Our data thus provide new support for a unified picture of β in the CPP-MR and bulk alloys. We also derive a short spin-diffusion length in NiCr,
85(1999); http://dx.doi.org/10.1063/1.370501View Description Hide Description
A new method is described for measuring the loss of spin-direction memory (spin relaxation) in nonmagnetic materials and at nonmagnetic interfaces. The method involves inserting the material of interest into an exchange-biased spin valve and monitoring the associated reduction in the spin valve’s magnetoresistancemeasured with the current perpendicular to the planes. This technique is tested by investigating spin relaxation near Nb/Cu interfaces. A surprisingly large loss per interface is found, between 15% and 25% with larger values being associated with thicker Nb layers.
85(1999); http://dx.doi.org/10.1063/1.370403View Description Hide Description
First principles local spin density calculations of the magnetic structure of interdiffused Cu/Py multilayers were performed. It was possible to solve the Kohn–Sham [Phys. Rev. 140, A1133 (1965)] equations for both canted and collinear magnetic arrangements to a high level of convergence. We found multiple, metastable, noncollinear magnetic structures that showed a reduced contribution to the saturation magnetization consistent with roughly one “magnetic dead” layer per interface. These canted interface layers were stable with respect to collinear interfaces by about 2 mRy per atom at the interface. The calculated noncollinear total spin magnetic moments as a function of the number of Py layers were in good agreement with the experiment.
Calculations of current-perpendicular-to-plane giant magnetoresistance with a current-conserving method85(1999); http://dx.doi.org/10.1063/1.370404View Description Hide Description
We present a current-conserving method to calculate the current-perpendicular-to-plane conductivity using Kubo’s formula in magnetic superlattices. We use this method to study the interfacescattering in Co/Cu (111) superlattices with different sources of scattering: clean interfaces with Fermi surface mismatch, spin-independent, and spin-dependent impurities. We find significant changes to the density-of-states under moderate impurity scattering.
85(1999); http://dx.doi.org/10.1063/1.370405View Description Hide Description
We report on electrical resistivitymeasurements for an single crystal in the temperature range 4.2–140 K and magnetic fields up to 8.4 T parallel to the c axis. The anomalies in the temperature and field dependencies of the resistivity are associated with magnetic phase transitions and allow one to complete the magnetic phase diagram. The relationship between the electrical resistivity and the periodicity of particular magnetic phases is discussed in light of magnetoresistance behavior in other antiferromagnetic U compounds.