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  • 1
    Electronic Resource
    Electronic Resource
    Magnetization reversal in systems of interacting magnetically hard particles (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3960-3964 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new procedure for investigating the switching behaviour of differently oriented particles in polycrystalline samples is introduced where the particle interaction is taken into account by the mean demagnetizing field. Based on specific remanence measurements the angular and field dependence of the probability of irreversible magnetization reversals (switching) is determined. This includes also the switching field distribution (SFD) of the material. The procedure is applied to a barium ferrite sample compacted from small particles. Due to the interaction the angular dependent switching fields are shifted to lower values compared to those predicted by the Stoner–Wohlfarth model and those measured for a strongly diluted sample, whereas the SFD is changed only slightly. This result as well as measurements of the initial susceptibility confirm single–domain particle behaviour of this material. Starting from our result for the switching probability it is shown that the angular dependence of the switching field can be deduced from angular dependent measurements of remanence coercivity only for samples with a very high degree of grain alignment. The determined probability is confirmed by comparing calculated and measured field dependence of the conventional remanence for the investigated material. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358578
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  • 2
    Electronic Resource
    Electronic Resource
    Comparison of magnetic methods for the determination of texture of permanent magnets : The 6th joint magnetism and magnetic materials (MMM)−intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6268-6270 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The singular point detection (SPD) technique as well as a least-mean-square procedure of fitting trial texture functions to demagnetization curves (DMC) were applied in order to determine the orientation density of the tetragonal axes of the Nd2Fe14B crystallites in sintered Nd-Fe-B magnets with different degrees of grain alignment. Both methods are less complicated than calculating the texture function from x-ray-diffraction data. The orientation densities obtained by both methods agree fairly. Analytically, they can be described as a Gaussian or a sum of cosine-power functions of the angle between the local tetragonal axis and the texture axis. This agreement is a test for the DMC method which can also be used for materials showing much larger anisotropy fields than the maximum available measuring field. The SPD and DMC methods can also be applied to measure the temperature dependence of the anisotropy field HA of the magnetic main phase in noncompletely textured polycrystalline materials. By means of the DMC method additionally the spontaneous polarization Js as well as the anisotropy constants K1 and K2 can be determined. As expected, the values of HA of our sintered Nd-Fe-B samples, measured up to 140 °C, are nearly independent of the degree of texture and are in agreement with those reported in literature. This confirms that SPD as well as DMC can be used to measure intrinsic magnetic properties for materials which can hardly be prepared as single crystals, such as interstitial compounds made by gas–solid reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358301
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  • 3
    Electronic Resource
    Electronic Resource
    Design optimization for a SmCo-biased colossal magnetoresistive thin film device (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5350-5352 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A device structure composed primarily of a film made from colossal magnetoresistive (CMR) material and a permanent magnet (PM) film used for biasing the CMR film is proposed as a sensor for magnetic objects. The PM film provides a magnetic field through the CMR film, which is substantially decreased when a magnetic object approaches the device, as part of the magnetic flux is now diverted through the object. To test the feasibility of this concept, we performed simulations of the magnetic field distribution with a three-dimensional finite boundary program. Our vertical model structure consists of a strip of CMR material covered by a PM strip with magnetic in-plane texture and magnetized along its width. The maximum possible biasing field through the CMR material is mainly controlled by the thickness to width ratio of the PM material and cannot be improved by the use of a soft magnetic cladding. The same effect is observed on the flux reduction by approaching a magnetic object. Preliminary results on an experimental realization of the device are given. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373344
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic interactions in nanometer-scale particle arrays grown onto permalloy films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7010-7012 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic interactions in arrays of nanometer-scale ferromagnetic iron particles enhanced by direct growth onto thin permalloy films were investigated. The magnetic measurements [Hall magnetometry up to 100 K and variable field MFM (magnetic force microscopy) at room temperature] showed that the magnetization behavior of the permalloy was strongly influenced by the presence of the small (∼13 nm in diameter) particles. The mean values of the particles' switching fields coincided with those for noninteracting particles. The switching field distribution of the iron particles, however, was considerably broadened by their interactions. These results for strongly interacting small particles exemplify the magnetization behavior of ever smaller and more dense magnetic storage media. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372914
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetism of nanometer-scale iron particles arrays (invited) (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5249-5254 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetization behavior in arrays of small ferromagnetic iron particles is investigated. Arrays were fabricated by a combination of chemical vapor deposition and scanning tunneling microscopy. This method allows a variety of particle arrays to be grown differing in particle height, diameter, or arrangement. Moreover, the arrays can be grown directly onto different materials such as Au or permalloy. Magnetic measurements were conducted by Hall magnetometery up to 100 K and compared to switching field measurements by means of magnetic force microscopy at room temperature. The magnetization reversal mechanisms were studied from magnetization curves measured for an arbitrary angle cursive-theta of the applied field with respect to the long axis of the particles. By analyzing the reversible rotation, the particles' magnetic core diameter and the shape anisotropy could be determined. A phenomenological model based on thermally activated magnetization reversal was introduced and compared to experimental switching field dependences on temperature as well as on cursive-theta. Thermal effects may govern the magnetization reversal in particles of 10 nm diameter at all temperatures. For 14 nm particles and temperatures below 30 K, curling (for cursive-theta≤30°) and homogeneous reversal modes appear to dominate. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369957
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of ion-irradiation-induced disorder on the low-field magnetoresistance of La0.67A0.33MnO3 (A=Sr, Ca) (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4791-4793 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on a systematic study of the correlation between the disorder produced by ion irradiation and the magnetoresistance (MR) behavior of two doped manganite films: a highly textured La0.67Sr0.33MnO3 film on a (100) LaAlO3 substrate and a film of La0.67Ca0.33MnO3 on a YSZ substrate with a high degree of large-angle grain boundary disorder. The films were grown via metal organic chemical vapor deposition and exposed to irradiation of 200 keV Ne ions. The temperature and field dependence of the resistivity were measured on the same samples at different levels of damage. For the Sr-doped film, the bulk magnetic properties were observed to degrade faster with cumulative damage than transport. For both films at low temperature, a low-field hysteretic MR was either induced or enhanced by ion damage. These effects are discussed in terms of diffusive transport through "granular" magnetically disordered regions. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370483
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  • 7
    Electronic Resource
    Electronic Resource
    On the angular and field distribution of the magnetization reversal in hard magnets (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5358-5362 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A measuring procedure for the determination of the switching behavior of hard magnetic particles is presented. For this end, the remanence vector is determined for increasing fields. In the first part of the presented analysis, the angular dependence of the switching field is calculated, neglecting the switching field distribution. In the second part, the portion of switching particles depending on the strength of the applied field and its orientation with respect to the particle easy axes is determined. This switching portion includes information on the angular dependence of the switching field and the switching field distribution for each particle orientation. The method is demonstrated on a magnetically diluted barium ferrite sample with noninteracting single-domain particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351974
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  • 8
    Electronic Resource
    Electronic Resource
    Immobilization diffusion in R2Fe17 nitrides : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6896-6898 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusion of nitrogen in R2Fe17 intermetallics is investigated by an approach which reconciles the solid-solution and immobilization theories of nitrogen diffusion. It turns out that two-sublattice diffusions may yield sharp concentration profiles but leave the phase structure of the nitride unchanged. Beside the reaction time and a local relaxation time there exists a global relaxation time which governs the smoothing of concentration gradients. Due to the large number of unknown energy parameters involved it is difficult to make quantitative predictions, but in general the diffusion behavior depends on factors such as the use of N2 or NH3 as a nitrogen source. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367767
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  • 9
    Electronic Resource
    Electronic Resource
    Grain boundary effects on transport in metalorganic chemical vapor deposition-grown, Ca-doped lanthanum manganites : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7055-7057 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transport properties of metalorganic chemical vapor deposited films of lanthanum manganite grown on various substrates are investigated. The more disordered films show a magnetoresistance that is both large and relatively temperature independent over a wide temperature range. At low magnetic fields, a linear field dependence is observed and is attributed to spin-polarized intergrain tunneling. In addition, at low fields a hysteretic dependence of resistivity on the magnetic field has been observed. This effect has been attributed to the scattering of spin-polarized carriers at the grain boundary. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367548
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  • 10
    Electronic Resource
    Electronic Resource
    Erratum: "Hall cross size scaling and its application to measurements on nanometer-size iron particle arrays" [Appl. Phys. Lett. 76, 3283 (2000)] (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 762-762 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.127111
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