Negative spin-valve effect inCo65Fe35/Ag/

C. Bellouard¹,

HD Rapp²,

B. George³

et al.

Abstract

A minimum of the magnetoresistance under low fields has been observed with a Co 65 Fe 35 /Ag/ ͑Co 65 Fe 35 ͒ 50 Gd 50 trilayer at 4.2 and 300 K. This negative spin-valve effect is explained by the scattering of the conduction electrons by the Co or Fe moments included in two different structures: a polycrystalline ͑Co 65 Fe 35 ͒ and an amorphous one ͓͑Co 65 Fe 35 ͒ 50 Gd 50 ͔. The Gd moments allow one to control the magnetic configuration of the transition-metal moments of the layers but are inefficient for the magnetoresistance. This interpretation is confirmed by measurements using high pulsed fields.

Enhanced exchange and reduced magnetization of Gd in an Fe/Gd/Fe trilayer

“…2 The alloys of RE and TM can also lead to negative mangetoresistance (MR) in a structure, as the alignment of its magnetic moment with the external magnetic field will depend on the proportion of RE and TM. Typical examples for this are the Gd 1−x Co x and Gd 1−x (CoFe) x alloys, [3][4][5] whose magnetic moment and spin polarization can be adjusted with the composition. 6 Other recent applications of REs and their alloys are the reduction of spin-transfer noise in reading heads, 7 tuning the resonance of a magnetic domain wall, 8 and the nucleation and characterization of an in-plane magnetic domain wall.…”

Thermally assisted writing for perpendicular MRAM

“…2. The GMR ratio increased with increasing Co 90 Fe 10 thickness for thickness less than 0.9 nm.Since 4f electrons have little contribution to the differential spin scattering [9,10], the GMR effect in ferrimagnetic spin valves is mainly contributed from the 3d sub-lattice. The inserted Co 90 Fe 10 layer increased differential spin scattering at interfaces so the GMR ratios first increased with increasing Co 90 Fe 10 thickness.…”

Unconventional GMR angular dependence using a compensated ferrimagnet

“…At low temperature, an inverse giant magnetoresistance effect is observed as measured by Bellouard et al using a Gd-rich GdFeCo electrode [3]. In this temperature range the cobalt magnetisation is antiparallel to the GdCo magnetisation.…”

“…For such spin torque devices, compensated ferrimagnetic alloys such as GdCo have already been shown to be interesting model systems [9]. Their spin polarisation is large enough to get magnetoresistive effects [3] and they can be tuned by changing the temperature [8]. Their magnetic anisotropy can also be designed to induce out-of-plane or in-plane easy-axis depending on deposition conditions and heat treatments.…”