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Galvano-magnetic thin film sensors (abstract) (1985)

Hoffmann, Horst

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 57 (1985), S. 3831-3831

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Magnetoresistance detectors are used to observe the magnetic state of microscopic parts of magnetized samples. The planar Hall effect can be used instead. Both effects can be applied to find out the logic "1'' or "0'' state of magnetic storage devices. They also can be used for a quantitative and sensitive measurement of magnetic fields as well as a magneto-elastic strain gauge. Soft magnetic permalloy films are appropriate for the field detection while amorphous Fe1−xBx films are suitable for the strain measurements. The sensor films have to show a uniaxial anisotropy. The strength of it determines the range of the detectable fields and strains. The sensitivity of the magnetoresistance emr=dΔU/dH=2( ρ⊥−ρ(parallel)) 1/db JH/HK2(V/Oe) depends linearly on the magnetic field H applied along the hard axis. l, d, b are the film length, thickness and width, respectively. The sensitivity of the planar Hall effect, which is given by epl=dUpl/dH =( ρ(parallel)−ρ⊥)s/db J(1/HK) is independent of the applied field along the hard axis as long as H(very-much-less-than)HK. s is the separation of the Hall contacts. Both sensitivities are reciprocal to the uniaxial anisotropy, HK as long as the applied field, H is smaller than HK. The theoretically expected sensitivity usually is decreased by domain splitting and the influence of the magnetization ripple. The smaller HK is (the larger the sensitivity is) the stronger is the influence of the ripple. It gives an upper limit of the interval in which external fields or applied strains can be quantitatively measured. Double layered films can prevent the domain splitting. The sensor theory including the ripple and experimental data will be given.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.334937

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Digitale Medien

HF sputtered indium oxide films doped with tin (1978)

Hoffmann, Horst ; Dietrich, A. ; Pickl, J. ; [weitere]

Springer

Applied physics 16 (1978), S. 381-390

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ISSN: 1432-0630

Schlagwort(e): 73 ; 72.20

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau , Physik

Notizen: Abstract Indium-tin-oxide films (ITO films) sputtered in Ar-atmosphere with and without addition of oxygen reveal an irreversible increase in conductivity during annealing in vacuum. This annealing process increases drastically the density of free electrons, while the Hall mobility changes only slightly. Below the annealing temperature the temperature dependence of the conductivity is reversible. In films with low density of free electrons, which behave like non-degenerated semiconductors, two activation energies for the mobility could be found. The irreversible changes, observed during annealing in the vacuum, are explained by diffusion of oxygen from the interior of the film to the surface, followed by desorption of the oxygen from the surface into the vacuum. The excess oxygen in the non-stoichiometric films plays the role of electron traps. The irreversible effects during annealing in the vacuum are partly reversible in the long run. If the annealed films are exposed to oxygen or air their conductivity decreases because of diffusion of oxygen from the surface into the film.