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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 422 (2003), S. 701-704 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Inverse freezing and inverse melting are processes where a more symmetric phase is found at lower temperatures than at higher temperatures. Such inverse transitions are very rare. Here we report the existence of an inverse transition effect in ultrathin Fe films that are magnetized ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: With pulsed lasers as light sources, a new and important element is added to photoemission: time resolution. In order to make use of the high light intensities available, the experiment should measure the spin polarization of the total photoyield since this quantity is insensitive to space-charge effects. The following examples are discussed: (1) For amorphous GdTbFe, a magneto-optical storage material, it is shown that the speed of thermomagnetic writing critically depends on whether the initial temperature of the sample is above or below the compensation temperature. (2) The response of the magnetic order to pico- and nanosecond heating pulses has been measured in iron and other materials. It is found that the spin polarization of the electrons emitted from Fe by 30-ps pulses does not depend on the pulse energy even if melting occurs. Accordingly, ferromagnetic relaxation in Fe takes place on a time scale which is considerably longer than 30 ps. (3) Using optical spin orientation, the dynamics of the band bending induced by high-intensity laser pulses has been studied in a p-GaAs/Cs Schottky barrier. The buildup time for the photovoltage created by the electron-hole pairs excited in the band-bending region is of the order of several hundred picoseconds.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4438-4440 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use time-resolved spin-polarized photoemission to investigate thermomagnetic writing of domains in magneto-optic media, focusing on the relaxation time of the magnetization and the dynamic behavior of the nucleation process. In our initial studies, we examine a 90-nm-thick GdTbFe film using a pulsed excimer laser (pulse duration: 16 ns) as the light source for the photoemission process. We find that the thermomagnetic switching behavior is different above and below the compensation temperature Tcomp. When the sample temperature is held above Tcomp, the spin polarization of the electrons emitted during the writing pulse has the sign of the initial state even though subsequent examination shows that a reversed magnetization domain has been formed. Therefore, the domain is thermomagnetically nucleated during the trailing edge of the 16 ns writing pulse or even later when the irradiated domain cools down. On the other hand, if the initial temperature is slightly below Tcomp, the electrons emitted during the writing pulse have reversed polarization showing that the reversal of the magnetization takes place quickly compared to the pulse duration. This difference shows that compensation-point writing is much faster than Curie-point writing. Based on these measurements we propose a model to interpret the different thermomagnetic switching processes which take place above and below Tcomp. The results can be explained by different thermal relaxation times between the excited electrons and the lattice and between the electrons and the spin system.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2800-2804 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new ultrahigh vacuum instrument allowing in situ Kerr microscopy and scanning tunneling microscopy is described. The Kerr microscope has a spatial resolution of about 1 μm. First experimental results are reported on the magnetism of a 5 μm wide stripe consisting of six atomic layers of Fe grown in situ by molecular beam epitaxy on a W(110) surface. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5099-5101 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the magnetization of in-plane magnetized ultrathin magnetic dots of Co on Cu(100) as a function of temperature and applied field by scanning Kerr microscopy. Co dots with lateral sizes down to 4 μm and a thickness of 1.8 atomic layers show a sharp magnetic phase transition which is indistinguishable from the one of extended films. The scaling plot suggests that these small particles belong to the Ising universality class. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 6166-6168 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated ultrathin Co particles with various shapes, variable thicknesses δ (2 ML〈δ〈22 ML), and lateral size L ranging from 100 μm to (approximate)100 nm. We find that all particles are magnetized in-plane at room temperature and are in a single domain state, independently of shape and size—with some remarkable exceptions. We also find that the magnetic state of a particle can be manipulated without influencing the state of the neighbors. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5321-5324 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin epitaxial iron overlayers and sandwiches on Cu(001) have been investigated by spin-polarized photoemission. The magnetization was measured as a function of perpendicularly applied field and temperature. Up to 14 monolayers (ML) of iron grow epitaxially on Cu(001) in the fcc phase and are ferromagnetic. At 30 K a remanence magnetization perpendicular to the plane of the film is observed for both the Fe/Cu(001) and the Cu/Fe/Cu(001) systems with Fe layers thicker than 2 ML. The coercive field, measured as function of temperature for a 10-ML Fe film, decreases rapidly from 2.7 kOe at 30 K to about 50 Oe at 200 K. The Curie temperature is 300 K for films thicker than 8 ML and increases for thinner films up to 500 K. The transition from fcc to bcc iron occurs at 15 ML. It is recognized by a jump of the Curie temperature to 1000 K and by the disappearance of the remanence magnetization at 30 K. Simultaneous evaporation of Fe and Cu at various rates also results in epitaxial overlayers with characteristic magnetic features. The fcc Fe films are suitable for thermomagnetic recording. Writing and reading has been carried out by a UV excimer laser. Reading was performed by analyzing the sign of the spin polarization of the photoelectrons.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5331-5333 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial bcc Fe films, grown on Ag(001), ranging from 0.8 to 10 monolayers (ML), are ferromagnetic. At 30 K a remanent magnetization along the surface normal is observed for the 3–4-ML films. No perpendicular remanence is observed for the same films above 100 K and for films thicker than 5 ML or thinner than 2 ML. Above 5 ML the Curie temperature is around 1000 K as for bulk bcc Fe; for thinner films it is reduced and amounts to 400 K only for the 1 ML film.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5661-5663 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spin polarization of the photoelectrons emitted from Sn and Fe during picosecond (ps) and nanosecond (ns) laser pulses is measured as function of the laser intensity. For Sn the optically induced spin polarization is defined through the lattice symmetry. No difference is found between ps and ns heating. From this it is concluded that the melting of a metal like tin occurs on a time scale which is short compared to the duration of a 70 ps laser pulse. In Fe the spin polarization probes the magnetic order. It is found that Fe cannot be demagnetized within the duration of a 30 ps laser pulse, even if the melting point is reached in the laser focus. During a ns laser pulse the spin system and the lattice are in thermal equilibrium.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2528-2530 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The scanning tunneling microscope is used to study arsenic precipitates in low-temperature-grown and annealed GaAs. Tunneling spectroscopy reveals a distribution of states throughout the band gap, arising from the precipitates, with the density of midgap states increasing as the precipitate size increases. The Fermi level is found to be pinned at EV+0.65 eV for 600 °C annealed material. For 800 °C annealed material the Fermi level is located at EV+1.05 eV in regions far from precipitates, and additional depletion regions are observed near the precipitates.
    Type of Medium: Electronic Resource
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