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Papers by John Slonczewski

Research paper thumbnail of Origin of Magnetic Anisotropy in Cobalt-Substituted Magnetite

Physical Review, 1958

ABSTRACT

Research paper thumbnail of Band Structure of Graphite

Physical Review, 1958

Tight-binding calculations, using a two-dimensional model of the graphite lattice, lead to a poin... more Tight-binding calculations, using a two-dimensional model of the graphite lattice, lead to a point of contact of valence and conduction bands at the corner of the reduced Brillouin zone. A perturbation calculation which starts with wave functions of the two-dimensional lattice and is applied ...

Research paper thumbnail of Theory of Magnetostriction in Cobalt-Manganese Ferrite

Physical Review, 1961

ABSTRACT

Research paper thumbnail of Theory of the Dynamical Jahn-Teller Effect

Physical Review, 1963

ABSTRACT

Research paper thumbnail of Measurement of the spin-transfer-torque vector in magnetic tunnel junctions

Nature Physics, 2007

The transfer of spin angular momentum from a spin-polarized current to a ferromagnet can generate... more The transfer of spin angular momentum from a spin-polarized current to a ferromagnet can generate sufficient torque to reorient the magnet’s moment. This torque could enable the development of efficient electrically actuated magnetic memories and nanoscale microwave oscillators. Yet difficulties in making quantitative measurements of the spin-torque vector have hampered understanding. Here we present direct measurements of both the magnitude

Research paper thumbnail of Raman scattering and phase transitions in stressed SrTiO3

Solid State Communications, 1971

Research paper thumbnail of Zeeman effect in dynamic Jahn-Teller impurities

Solid State Communications, 1969

Numerical computations show that Ham's reduction factor q varies between the narrow limits 0.484 ... more Numerical computations show that Ham's reduction factor q varies between the narrow limits 0.484 <q < 1/2, for strongly coupled E-states. This means that anisotropic parts of the g-factor and hyperfine splitting depend negligibly on warping of the adiabatic potential.

Research paper thumbnail of Current-driven excitation of magnetic multilayers

Journal of Magnetism and Magnetic Materials, 1996

A new mechanism is proposed for exciting the magnetic state of a ferromagnet. Assuming ballistic ... more A new mechanism is proposed for exciting the magnetic state of a ferromagnet. Assuming ballistic conditions and using WKB wave functions, we predict that a transfer of vectorial spin accompanies an electric current flowing perpendicular to two parallel magnetic films connected by a normal metallic spacer. This spin transfer drives motions of the two magnetization vectors within their instantaneously common plane. Consequent new mesoscopic precession and switching phenomena with potential applications are predicted.

Research paper thumbnail of Overview of interlayer exchange theory

Journal of Magnetism and Magnetic Materials, 1995

Basic mechanisms of interlayer exchange coupling between two ferromagnets separated by a non-magn... more Basic mechanisms of interlayer exchange coupling between two ferromagnets separated by a non-magnetic spacer are surveyed. Simple generic theoretical models yielding closed formulae are treated. First, intrinsic exchange between itinerant ferromagnets is treated in the free-electron band approximation, including corrections to the elementary sinusoidal dependences on metallic-spacer thickness and on angle theta included between the magnetic moments. Properties of metallic and insulating spacers are compared. Then three special mechanisms of non-cos theta coupling are described: (1) fluctuations of spacer thickness, (2) loose spins, and (3) a novel phenomenological coupling through a non-normal spacer, possibly acting in spacers composed of chromium or manganese.

Research paper thumbnail of Mechanism of interlayer exchange in magnetic multilayers

Journal of Magnetism and Magnetic Materials, 1993

ABSTRACT

Research paper thumbnail of Standing waves of wall vibration

Journal of Magnetism and Magnetic Materials, 1983

The forced vibrations of an infinite chain of coupled masses with long-range interactions is anal... more The forced vibrations of an infinite chain of coupled masses with long-range interactions is analyzed. Calculations explain the standing wave patterns observed by Spreen and Argyle in an array of plane parallel 180 ° domain walls pinned by a pair of cracks in a garnet film.

Research paper thumbnail of Theoretical investigation of the relationship between spin torque and magnetoresistance in spin-valves and magnetic tunnel junctions

Journal of Magnetism and Magnetic Materials, 2007

A theoretical study is presented concerning the relationship between spin transfer torque and abs... more A theoretical study is presented concerning the relationship between spin transfer torque and absolute current-perpendicular-to-plane magnetoresistance in metallic spin-valves (SV) and magnetic tunnel junctions. In a first step, using Valet and Fert Boltzmann-like theory extended to any metallic magnetic multilayers with non-collinear magnetizations, linear relationships between spin torque and absolute current-perpendicular-to-plane giant magnetoresistance are derived numerically, when varying the parameters of the structure one by one. The obtained results are compared with an extension of J.C. Slonczewski's circuit theory. The latter model gives an analytical expression of this linear dependence. In a second step, using an out-of-equilibrium perturbation formalism (Keldysh technique), we study the tunnel magnetoresistance (TMR) dependence of the spin torque amplitude in magnetic tunnel junctions when varying the parameters one by one in the junction. Once again, linear dependences are obtained, with different characteristics when the TMR vanishes. It is shown that these two equivalent behaviours are associated with different origins of the spin torque. r

Research paper thumbnail of Force, momentum and topology of a moving magnetic domain

Journal of Magnetism and Magnetic Materials, 1979

Research paper thumbnail of Modes of natural vibration for magnetic domains

Journal of Magnetism and Magnetic Materials, 1981

ABSTRACT

Research paper thumbnail of Threshold current for spin-transfer switching

Journal of Magnetism and Magnetic Materials, 2004

ABSTRACT

Research paper thumbnail of Interaction of Elastic Strain with the Structural Transition of Strontium Titanate

Physical Review B, 1970

... VOLUME 1, NUMBER 9 Interaction of Elastic Strain with the Structural Transition of Strontium ... more ... VOLUME 1, NUMBER 9 Interaction of Elastic Strain with the Structural Transition of Strontium Titanate* JC SLONCZEWSKI IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598 AND H. THOMAS IBM Zurich Research Laboratory, Riischlikon, Switzerland ...

Research paper thumbnail of DOMAIN WALL MOTION IN RARE-EARTH SUBSTITUTED Ga:YIG EPITAXIAL FILMS

Research paper thumbnail of Resume of Classical Magnetism and Bubble Domain Statics

Magnetic Domain Walls in Bubble Materials, 1979

Research paper thumbnail of Analysis of Stress and Temperature Dependence of Fluorescence in SrTi O 3 : Cr 3 +

Physical Review B, 1970

We write a configurational potential for SrTiO3 which depends on strain and the soft optic-mode c... more We write a configurational potential for SrTiO3 which depends on strain and the soft optic-mode coordinates whose wave vector lies at the corner of the Brillouin zone. Minimizing this potential gives the static response of the crystal to applied stress. Below the cubic-to-tetragonal transition temperature at 106°K, uniaxial stress applied in the [111] direction induces a transition from the natural tetragonal to a trigonal phase, but transitions for [100] and [110] stresses are not found. A crystal-field calculation gives the R-line emission energy of Cr3+ impurities. The results fit the temperature-dependence anomaly found by Stokowsky and Schawlow and, within limits, the pressure dependence found by Burke and Pressley. However, pronounced discrepancies appear at stresses along the [100] and [110] directions which exceed critical values of 10 and 57 kg/mm2, respectively, suggesting that new phases of unknown character appear. The crystal-field parameter values inferred from the comparison with experiment support the nearest-neighbor approximation for the cubic component of the crystal-field, but not for lower-symmetry components. Our calculations disagree with a reported measurement of the stress dependence of the transition temperature.

Research paper thumbnail of Gradientless Propulsion and State Switching of Bubble Domains

We investigate a class of phenomena which we call bubble automotion whereby a bubble or a bubble ... more We investigate a class of phenomena which we call bubble automotion whereby a bubble or a bubble lattice is propelled by a time-modulated field which is homogeneous rather than by locally applied field gradients. Linear translation of certain kinds of bubbles occurs when bias modulation Hb+hz(t) having certain amplitudes and large |dhz/dt| is superimposed on a steady in-plane field Hip which is less than Hb. Pulsed hz excitations produce characteristic automotion vectors that can uniquely distinguish for the first time among certain wall states (S,L,P) having a common winding number S but different arrangements of L Bloch lines and P Bloch points. A pair of S=1 bubbles we call sigma+ and sigma-, translate typically one micron per pulse in opposite directions orthogonal to Hip, i.e., parallel to +/-Hb==> × Hip==>. A model consistent with our measurements has the static configurations (1,2,0)+ and (1,2,0)- where the +/- refers both to the direction of automotion and the two arrangements (N+, S-) and (N-,S+) of Bloch line polarity and sense of twist. The automotion arises because the translational coercive force couples to motions of the wall radius and the Bloch lines. Unichiral bubbles chi+/-=(100)+/- of either handedness (+/-) do not automote. Excitations outside the range for automotion can cause changes in wall structure. We show how to switch at will among sigma-, +, chi- and chi+ states.

Research paper thumbnail of Origin of Magnetic Anisotropy in Cobalt-Substituted Magnetite

Physical Review, 1958

ABSTRACT

Research paper thumbnail of Band Structure of Graphite

Physical Review, 1958

Tight-binding calculations, using a two-dimensional model of the graphite lattice, lead to a poin... more Tight-binding calculations, using a two-dimensional model of the graphite lattice, lead to a point of contact of valence and conduction bands at the corner of the reduced Brillouin zone. A perturbation calculation which starts with wave functions of the two-dimensional lattice and is applied ...

Research paper thumbnail of Theory of Magnetostriction in Cobalt-Manganese Ferrite

Physical Review, 1961

ABSTRACT

Research paper thumbnail of Theory of the Dynamical Jahn-Teller Effect

Physical Review, 1963

ABSTRACT

Research paper thumbnail of Measurement of the spin-transfer-torque vector in magnetic tunnel junctions

Nature Physics, 2007

The transfer of spin angular momentum from a spin-polarized current to a ferromagnet can generate... more The transfer of spin angular momentum from a spin-polarized current to a ferromagnet can generate sufficient torque to reorient the magnet’s moment. This torque could enable the development of efficient electrically actuated magnetic memories and nanoscale microwave oscillators. Yet difficulties in making quantitative measurements of the spin-torque vector have hampered understanding. Here we present direct measurements of both the magnitude

Research paper thumbnail of Raman scattering and phase transitions in stressed SrTiO3

Solid State Communications, 1971

Research paper thumbnail of Zeeman effect in dynamic Jahn-Teller impurities

Solid State Communications, 1969

Numerical computations show that Ham's reduction factor q varies between the narrow limits 0.484 ... more Numerical computations show that Ham's reduction factor q varies between the narrow limits 0.484 <q < 1/2, for strongly coupled E-states. This means that anisotropic parts of the g-factor and hyperfine splitting depend negligibly on warping of the adiabatic potential.

Research paper thumbnail of Current-driven excitation of magnetic multilayers

Journal of Magnetism and Magnetic Materials, 1996

A new mechanism is proposed for exciting the magnetic state of a ferromagnet. Assuming ballistic ... more A new mechanism is proposed for exciting the magnetic state of a ferromagnet. Assuming ballistic conditions and using WKB wave functions, we predict that a transfer of vectorial spin accompanies an electric current flowing perpendicular to two parallel magnetic films connected by a normal metallic spacer. This spin transfer drives motions of the two magnetization vectors within their instantaneously common plane. Consequent new mesoscopic precession and switching phenomena with potential applications are predicted.

Research paper thumbnail of Overview of interlayer exchange theory

Journal of Magnetism and Magnetic Materials, 1995

Basic mechanisms of interlayer exchange coupling between two ferromagnets separated by a non-magn... more Basic mechanisms of interlayer exchange coupling between two ferromagnets separated by a non-magnetic spacer are surveyed. Simple generic theoretical models yielding closed formulae are treated. First, intrinsic exchange between itinerant ferromagnets is treated in the free-electron band approximation, including corrections to the elementary sinusoidal dependences on metallic-spacer thickness and on angle theta included between the magnetic moments. Properties of metallic and insulating spacers are compared. Then three special mechanisms of non-cos theta coupling are described: (1) fluctuations of spacer thickness, (2) loose spins, and (3) a novel phenomenological coupling through a non-normal spacer, possibly acting in spacers composed of chromium or manganese.

Research paper thumbnail of Mechanism of interlayer exchange in magnetic multilayers

Journal of Magnetism and Magnetic Materials, 1993

ABSTRACT

Research paper thumbnail of Standing waves of wall vibration

Journal of Magnetism and Magnetic Materials, 1983

The forced vibrations of an infinite chain of coupled masses with long-range interactions is anal... more The forced vibrations of an infinite chain of coupled masses with long-range interactions is analyzed. Calculations explain the standing wave patterns observed by Spreen and Argyle in an array of plane parallel 180 ° domain walls pinned by a pair of cracks in a garnet film.

Research paper thumbnail of Theoretical investigation of the relationship between spin torque and magnetoresistance in spin-valves and magnetic tunnel junctions

Journal of Magnetism and Magnetic Materials, 2007

A theoretical study is presented concerning the relationship between spin transfer torque and abs... more A theoretical study is presented concerning the relationship between spin transfer torque and absolute current-perpendicular-to-plane magnetoresistance in metallic spin-valves (SV) and magnetic tunnel junctions. In a first step, using Valet and Fert Boltzmann-like theory extended to any metallic magnetic multilayers with non-collinear magnetizations, linear relationships between spin torque and absolute current-perpendicular-to-plane giant magnetoresistance are derived numerically, when varying the parameters of the structure one by one. The obtained results are compared with an extension of J.C. Slonczewski's circuit theory. The latter model gives an analytical expression of this linear dependence. In a second step, using an out-of-equilibrium perturbation formalism (Keldysh technique), we study the tunnel magnetoresistance (TMR) dependence of the spin torque amplitude in magnetic tunnel junctions when varying the parameters one by one in the junction. Once again, linear dependences are obtained, with different characteristics when the TMR vanishes. It is shown that these two equivalent behaviours are associated with different origins of the spin torque. r

Research paper thumbnail of Force, momentum and topology of a moving magnetic domain

Journal of Magnetism and Magnetic Materials, 1979

Research paper thumbnail of Modes of natural vibration for magnetic domains

Journal of Magnetism and Magnetic Materials, 1981

ABSTRACT

Research paper thumbnail of Threshold current for spin-transfer switching

Journal of Magnetism and Magnetic Materials, 2004

ABSTRACT

Research paper thumbnail of Interaction of Elastic Strain with the Structural Transition of Strontium Titanate

Physical Review B, 1970

... VOLUME 1, NUMBER 9 Interaction of Elastic Strain with the Structural Transition of Strontium ... more ... VOLUME 1, NUMBER 9 Interaction of Elastic Strain with the Structural Transition of Strontium Titanate* JC SLONCZEWSKI IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598 AND H. THOMAS IBM Zurich Research Laboratory, Riischlikon, Switzerland ...

Research paper thumbnail of DOMAIN WALL MOTION IN RARE-EARTH SUBSTITUTED Ga:YIG EPITAXIAL FILMS

Research paper thumbnail of Resume of Classical Magnetism and Bubble Domain Statics

Magnetic Domain Walls in Bubble Materials, 1979

Research paper thumbnail of Analysis of Stress and Temperature Dependence of Fluorescence in SrTi O 3 : Cr 3 +

Physical Review B, 1970

We write a configurational potential for SrTiO3 which depends on strain and the soft optic-mode c... more We write a configurational potential for SrTiO3 which depends on strain and the soft optic-mode coordinates whose wave vector lies at the corner of the Brillouin zone. Minimizing this potential gives the static response of the crystal to applied stress. Below the cubic-to-tetragonal transition temperature at 106°K, uniaxial stress applied in the [111] direction induces a transition from the natural tetragonal to a trigonal phase, but transitions for [100] and [110] stresses are not found. A crystal-field calculation gives the R-line emission energy of Cr3+ impurities. The results fit the temperature-dependence anomaly found by Stokowsky and Schawlow and, within limits, the pressure dependence found by Burke and Pressley. However, pronounced discrepancies appear at stresses along the [100] and [110] directions which exceed critical values of 10 and 57 kg/mm2, respectively, suggesting that new phases of unknown character appear. The crystal-field parameter values inferred from the comparison with experiment support the nearest-neighbor approximation for the cubic component of the crystal-field, but not for lower-symmetry components. Our calculations disagree with a reported measurement of the stress dependence of the transition temperature.

Research paper thumbnail of Gradientless Propulsion and State Switching of Bubble Domains

We investigate a class of phenomena which we call bubble automotion whereby a bubble or a bubble ... more We investigate a class of phenomena which we call bubble automotion whereby a bubble or a bubble lattice is propelled by a time-modulated field which is homogeneous rather than by locally applied field gradients. Linear translation of certain kinds of bubbles occurs when bias modulation Hb+hz(t) having certain amplitudes and large |dhz/dt| is superimposed on a steady in-plane field Hip which is less than Hb. Pulsed hz excitations produce characteristic automotion vectors that can uniquely distinguish for the first time among certain wall states (S,L,P) having a common winding number S but different arrangements of L Bloch lines and P Bloch points. A pair of S=1 bubbles we call sigma+ and sigma-, translate typically one micron per pulse in opposite directions orthogonal to Hip, i.e., parallel to +/-Hb==> × Hip==>. A model consistent with our measurements has the static configurations (1,2,0)+ and (1,2,0)- where the +/- refers both to the direction of automotion and the two arrangements (N+, S-) and (N-,S+) of Bloch line polarity and sense of twist. The automotion arises because the translational coercive force couples to motions of the wall radius and the Bloch lines. Unichiral bubbles chi+/-=(100)+/- of either handedness (+/-) do not automote. Excitations outside the range for automotion can cause changes in wall structure. We show how to switch at will among sigma-, +, chi- and chi+ states.