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Magnetic and structural properties of multilayers involving magnetic and nonmagnetic thin films

Objective

IT IS PROPOSED TO INVESTIGATE THE STRUCTURAL AND MAGNETIC PROPERTIES OF (A) VERY THIN FILMS AND (B) MAGNETIC SUPERLATTICES OF, IN THE FIRST INSTANCE 3-D TRANSITION METALS (EG NI,FE) WITH METALLIC AND NON-METALLIC INTERFACES (EG OTHER TRANSITION ELEMENTS, NAF, NACL, MGO).
The motivation for this work was the potential to produce new magnetic materials with properties tailored to the needs of the magnetic storage industry. Efforts have been concentrated on sample production, morphology and interface effects, especially magnetic coupling between films.
THE LAST THREE MATERIALS ARE TYPICALLY USED FOR SUBSTRATES FOR EPITAXIAL FILM GROWTH. PRELIMINARY MICROWAVE SPECTROSCOPIC EXPERIMENTS ON IRON LAYERS EMBEDDED IN NICKEL FILMS ARE UNDER WASY. H PUSZKARSKI (PRIVATE COMMUNICATION) HAS PREDICTED THAT INTERNAL PINNING SHOULD LEAD TO CHARACTERISTICS SPIN WASVE EXCITATIONS WHICH SHOULD ALSO DEPEND ON THE LOCATION OF THE IRON LAYER. IN CASE (A) IT IS EXPECTED THAT IT WILL BE NECESSARY TO STACK A SEQUENCE OF VERY THIN FILMS IN ORDER TO ACHIEVE ADEQUATE SENSITIVITY FOR SOME MAGNETIC MEASUREMENTS. THE DISTINCTION BETWEEN SUCH A SYSTEM AND A SUPERLATTICE IS WHETHER MAGNETIC COUPLING DOES OR DOES NOT EXIST BETWEEN NEIGHBOURING MAGNETIC LAYERS.
3A WIDE RANGE OF ANALYTICAL TOOLS (ELECTRON MICROSCOPY, LEED,HEED, RHEED, AUGER SPECTROSCOPY INCLUDING DEPTH PROFILING) IS AVAILABLE TO THE PROPOSERS AND THERE IS AN UHV EVAPORATION PLANT FOR PRELIMINARY INVESTIGATIONS. HOWEVER THE GROWTH OF MULTILAYER FILMS, CONSISTING OF A LARGE NUMBER OF LAYERS, REQUIRES A MORE SOPHISTICATED UHV EVAPORATOR OFFERING RAPID AND REPEATED SWITCHING BETWEEN 2 OR 3 VERY STABLE EVAPORANT SOURCES IN CONDITIONS OF THE HIGHEST PURITY WITH IN SITU STRUCTURAL AND CHEMICAL ANALYSIS OF THE DEVELOPING LAYER STRUCTURE. SUCH FACILITIES ARE ONLY AFFORDED BY SYSTEMS EXPLOITING MODERN MOLECULAR BEAM EPITAXY (MBE) TECHNOLOGY, AND SUCH A SYSTEM FORMS PART OF THE EQUIPMENT SUBMISSION.

THE YORK GROUP HAS EXPERIENCE WHICH EXTENDS OVER MANY YEARS IN THE GROWTH AND EVALUATION OF THIN AND ULTRA-THIN METALLIC SINGLE CRYSTAL FILMS (11-15). FERROMAGNETIC NICKEL FILMS AND COPPER-NICKEL BICRYSTALS HAVE BEEN A PARTICULAR SUBJECT OF INVESTIGATION. THE GROUP WAS AMONGST THE FIRST TO PRESENT EXPERIMENTAL EVIDENCE AND A THEORY OF LAYER GROWTH USING AUGER ELECTRON SPECTROSCOPY AND ALLIED MICROSCOPIC AND DIFFRACTION TECHNIQUES (13), AND FIRAT TO REPORT THE UNUSUAL STRANSKI-KRASTENOV GROWTH MODE IN THE GROWTH OF THIN COPPER FILMS ON NICKEL (14,15). ADDITIONALLY DR PUCHALSKA'S GROUP (CNRS) HAS EXTENSIVE EXPERIENCE OF ELECTRON MICROSCOPY OF MAGNETIC FILMS AND DR LEVY'S GROUP IS CONCERNED WITH THE THEORETICAL STUDY OF MAGNETIC FILM STRUCTURES.

SINCE AN IMPORTANT FEATURE OF THE PROPOSED SYSTEMS IS THE STUDY OF LAYER-DEPENDENT MAGNETIC PROPERTIES, IT IS ESSENTIAL TO EMPLOY EXPERIMENTAL TECHNIQUES WHICH ARE SENSITIVE TO SUCH EFFECTS. MOSSBAUER SPECTROSCOPY CAN BE USED (16) IN THE CASE OF FE FILMS ALTHOUGH THIS PROVIDES INFORMATION ON THE LOCAL HYPERFINE FIELD AND CARE HAS TO BE EXERCISED IN DETERMINING THE MAGNETISATION. IT IS HOPED THAT SUCH INVESTIGATION WILL BE POSSIBLE IN DR J WILLIAMS'S GROUP AT SHEFFIELD UNIVERSITY. THE DYNAMIC MAGNETIC MEASUREMENTS USING MICROWAVE SPECTROSCOPY ARE ALSO SENSITIVE TO MAGNETISATION PROFILES (17,18) AND WORK ON INTERFACE EFFECTS ON THE SPIN WAVE SPECTRA OF NICKEL FILMS HAS BEEN CARRIED OUT IN DR WHITING'S GROUP (19,20). A MAJOR PART OF THE PROPOSAL IS THE APPLICATION OF THIS TECHNIQUE TO VERY THIN FILMS AND SUPERLATTICES. IN THE CASE OF THE LATTER, NEW FEATURES ARE EXPECTED AS A RESULT OF THE INTER-FILM COUPLING (10). HOWEVER IT IS NECESSARY TO COMPLEMENT DYNAMIC MAGNETIC MEASUREMENTS WITH STATIC ONES SUCH AS MAGNETOMETRY TO UNAMBIGUOUSLY DETERMINE CONTRIBUTIONS TO THE MAGNETIC PROPERTIES OF THE FILMS FROM MAGNETISATION, CRYSTALLINE AND SURFACE ANISOTROPIES, MAGNETOSTRICTION CRYSTALLINE AND DOMAIN STRUCTURE. STATIC MEASUREMENTS WILL BE CARRIED OUT IN DR PUCHALSKA'S GROUP AT CNRS AND SUPPORT IS SOUGHT FOR PURCHASING A MAGNETOMETER TO STRENGHTEN THIS ACTIVITY.

THIS GROUP HAS SPECIALIZED FOR MANY YEARS IN THE PHYSICS ON DOMAIN STRUCTURE AND MAGNETIC PROPERTIES IN THIN FILMS. SEVERAL METHODS OF OBSERVATION ARE USED; ELECTRON MICROSCOPY, BITTER TECHNIQUE, KERR AND FARADAY EFFECT WITH A DIGITAL IMAGE TREATMENT. IN THIN METALLIC FILMS (FE, NI, CO) AMORPHOUS LIKE GD CO, CO FE, NI CO P AND BUBBLE GARNETS HAVE BEEN A PARTICULAR SUBJECT OF INVESTIGATION (EG 21-28).

THE MATHEMATICAL ANALYSIS OF THE MULTILAYER COUPLING LEADS TO A WEA

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

University of York
Address
Heslington -
YO1 5DD York
United Kingdom

Participants (2)

Centre National de la Recherche Scientifique (CNRS)
France
Address
1 Place Aristide-briand
92195 Meudon
UNIVERSITE DE PARIS VII DENIS DIDEROT
France
Address
Place Jussieu 2
Paris