From spinwaves to Giant Magnetoresistance (GMR) and beyond P.A. - - PowerPoint PPT Presentation

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From spinwaves to Giant Magnetoresistance (GMR) and beyond P.A. - - PowerPoint PPT Presentation

Jan 17, 2023 178 likes •617 views

From spinwaves to Giant Magnetoresistance (GMR) and beyond P.A. Grnberg, Institut fr Festkrperforschung Forschungszentrum Jlich, Germany 1. Introduction 2. Discovery of BLS from Damon Eshbach surface modes 3. Discovery of interlayer

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1. Introduction 2. Discovery of BLS from Damon Eshbach surface modes 3. Discovery of interlayer exchange coupling 4. Discovery of Enhanced Magnetoresistance(GMR) 5. Further development:TMR and CIMS 6. Applications

From spinwaves to Giant Magnetoresistance (GMR) and beyond

P.A. Grünberg, Institut für Festkörperforschung Forschungszentrum Jülich, Germany

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1969: PhD in Darmstadt (Germany) with „Optical Spectroscopy and Crystal Field Analysis in some Rare Earth Garnets“ Mentor K.H.Hellwege, Supervisor: St.Hüfner 1969-1972 postdoctoral fellow at Carleton University Ottawa Canada. Raman Spectroscopy on electronic states and phonons Supervisor: J. A.Koningstein since 1972 Research Center Jülich, Institute for Magnetism founded in 1971 Investigation of magnetic semiconductors EuO, EuS Fabrication, magnetic and transport properties of layered magnetic structures Mentor: W.Zinn

May I introduce myself

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Bulk and Surface Spinwaves in EuO New instrumental development

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Page 186

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Coupled Damon-Eshbach-Spinwaves Landau Lifshitz equation ?

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M M

Pinhole coupling due to „magnetic bridges“ Orange peel or Neel type coupling caused by strayfields due to meandering interlayers

What was known in 1984 about interlayer coupling apart from the dynamic coupling?

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Coupled Damon-Eshbach-Spinwaves

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Effect of exchange coupling

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Coupled Damon-Eshbach-Spinwaves

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DE exch Argonne May 1985 1989

First measurement of interlayer exchange coupling as a function of the interlayer thickness

2 1 2 1 12

2 M M M M A Eexch ∗ ∗ − =

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Oscillatory coupling in Gd/Y multilayers (Majkrzak et al) Helical structures in Dy/Y multilayers (Salamon et al.) AF coupling in Fe/Cr/Fe layered structures (Grünberg et al) Work on interlayer exchange coupling published in 1986

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analogy: optical Fabry Perot interferometer

Fe/Cr/Fe Short period

  • scillations after

improvement

  • f growth

Fabry Perot model of interlayer exchange coupling

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Equivalent circuit ferromagnetic alloy M current Scattering event Mott`s two current model

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R

Coupled Fe/Cr/Fe structures

What can we expect in magnetic multilayers?

Fe Cr Fe M M Current

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First measurement of GMR

  • Phys. Rev. B 39, P. 4828, 1989

GMR AMR

Filing a patent: april 1988

R

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Le Creusot, August 1988

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Orsay Jülich

First measurements of GMR in Fe/Cr/Fe

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Boltzmann transport equation: Camley-Barnas model

First theories of GMR

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Current in Plane (CIP) D↑≈0.45 D↓≈ 0.08

λ↑≈λ↓ Theory and Experiment

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Giant Magneto- resistance (GMR)

  • sc.

Interlayer exchange coupling Tunnelingmagn- etoresistance (TMR) Mfree current induced magnetic excitations and switching (CIMS) Mfixed Mfree Mfixed

Spin dependent transfer phenomena in layered magnetic structures

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due to spin polarized currents

Mfixed Mfree

current induced magnetization switching and excitation of spinwaves proposed by J.Slonczewski and L.Berger in 1995

J.A. Katine et al., Phys. Rev. Lett. 84, 3149 (2000)

first experiment:

Mfixed Mfree

Start with ap alignment Start with par alignment

CIMS – advanced magnetic switching concept

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Four energetically nearly identical states give rise to two-step switching

T=5 K; Bext = 7.9 mT along hard axis

variable I fixed B

Mfixed Bext Mfree Ic1 Ic2

70 nm

Two step CIMS in Fe/Ag/Fe

R.Lehndorf, D.Bürgler, C.Schneider, Jülich 2007

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M Magnetization reversal of a thin-film element by a spin-polarized current M spin-polarized electric current precession spin-transfer torque damping

M Heff dMR dMp dMSTT

mx my mz

  • A. Kakay, R. Hertel, C.Schneider, IFF Jülich
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Applications

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by courtesy of NAOMI- Sensitech, Germany AF coupled multilayer: large signal (22-44%) easy tailoring of sensitivity unipolar Fig.13 working principle and data for GMR sensor with AF coupled multilayer

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GMR- Sensor

  • bject

permanent- magnet

N S

natural antiferro- magnet (NAF)

0 90 180 270 360

angle(°)

6 4 2

3.5nm Ta 4nm Ta ------------ cap layer 0.8nm CoFe 4nm CoFe------- pinned layer 4nm CoFe 5nm NiFe 2nm NiFe 2.5nm Cu ---------- spacer 0.8nm Ru 10nm IrMn----- NAF Si (substrate)

} }

}

free layer

SAF

buffer

}

GMR effect

bipolar synthetic antiferromagnet (SAF)

ΔR/RII (%)

Spinvalves Used in ABS- and ESP-Systems for cars

Here to monitor mechanical rotations

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micro hard disk drive

1991 2005

GMR sensors in read-heads for hard-disk drives

Shipment of GMR-read-heads (1997-2007):

5 billion (109)

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AFC media

AFC stabilising magnetic domains on hard disc

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nonvolatile information: TMR and MRAM (magnetic random access memory)

Conventional: writing by Oersted fields Advanced: writing by CIMS

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  • measurement of the Earth‘s

magnetic field in 2 or 3 axis

  • accuracy of 1°
  • low power consumption

(2 years battery life)

AMR-and GMR-Sensor Applications e.g. als Electronic Compass Combined with a Mobile GPS System For continous, retardation free alignment of map or direction of motion.

there are already mobiles on the market which include GPS, in future also compasses

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most vehicles contain parts of ferromagnetic materials traffic control indicate free parking lots on a display at the entrance of parkhouses

Traffic Control Sensors

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The motion of „Spirit and Opportunity“ on Mars are monitored by AMR sensors. Spirit and Opportunity

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e.g. Detection of piston end positions

The GMR-sensor detects - due to its high magnetic sensitivity - the position of the piston even at large distances and different cylinder diameters.

piston with magnet

GMR-sensor with processing

GMR-Field Sensor Applications

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bead

GMR in medicine and biology

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for read out in HDD can't be small enough for detecting magnetic beads: can't be large enough

New applications - New challenges

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information:

Thank Thank Thank You You You More More More Informations Informations Informations at at at www.fz www.fz www.fz-

  • juelich.de/gmr

juelich.de/gmr juelich.de/gmr

Hydra in tbe Greek mythology: cut one head, two new grow

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Y

magnetic nanoparaticles 10nm magnetic beads 1µ 10x10 Sensors on 0.1x0.1mm2 area see also „MRAM“ important ingredients

Y antibodies

good guys antigenes bad guys immune reaction

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system GMR[%] tmag[nm] ref. Fe/Cr/Fe 1.5 12 Fe/Cr/Fe 2 5 2) [Fe/Cr(1.2nm)]50 42 .45 2) Co/Cu/Co 15 3 3) [Co/Cu(0.9nm)]30 48 1.5 5) [Co/Cu(0.9)]16 65 1 6) 10 10 10 1) Co/Au/Co 1.8 1) Co/Cu/Co 2.0 1) Fe/Cu/Fe 0.5 1)

Largest GMR values in trilayers and multi layers at room temp

1) Grünberg et al.JMMM1991 2) Schad et al. JAP 1994 3)Egelhoff et al JAP79 4) Schad et al, Appl.Phys.Lett. 1994 5) Mosca et al JMMM 1991 6) Parkin Appl.Phys.Lett.1991

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recent example: M.Buchmeier et al. PRB 67(2003)184404 and phD thesis, Juelich 2003 Si

Fe Fe

evaluation includes twisting of magnetization in the Fe films

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Table 1: Comparison of interlayer coupling strengths for some structures with insulating, semiconducting, and metallic interlayers. Structure Interlayer thickness [nm] Coupling strength [mJ/m2] Reference Fe/MgO/Fe 0.5

  • 0.26

[12] Fe/Si/Fe 0.6

  • 6.2

[11] Co/Ru/Co <0.9

  • 5

[50] Fe/Cr/Fe 0.5

  • 1.6

[51]

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Le Creusot 1988

Le Creusot 1988 Europe

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