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  • 1
    Electronic Resource
    Electronic Resource
    Thermally stable spin valve films with synthetic antiferromagnet pinned by NiMn for recording heads beyond 20 Gbit/in.2 (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5720-5722 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal stability of spin valve films with synthetic antiferromagnet (SAF) pinned by antiferromagnetic IrMn, NiO, and NiMn layers were studied. The SAF layer enhances the thermal stability in general; however, the blocking temperature (and the blocking temperature distribution) of the antiferromagnet is still important for the magnetic rigidity of the pinned layer. Once the temperature reaches the blocking temperature the SAF layer can go into either the spin flip or flop state, depending upon the magnetic moment ratio of the reference layer and pinned layers. The GMR linear head response can be distorted for nonlinearity. The NiMn pinned SAF structure shows magnetic and thermal stability which makes it practical for the real products. A high GMR of 11% can be obtained in both bottom and top NiMn SAF spin valves by advanced processes. Recording heads were built using such stacks which demonstrated recording areal density of 20 Gbit/in.2 and beyond. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372500
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  • 2
    Electronic Resource
    Electronic Resource
    A study on pinned layer magnetization processes in different antiferromagnetic coupling systems of spin-valves (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5729-5731 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we report on magnetization reversal processes of pinned layers in different ferromagnetic and anti-ferromagnetic bilayer and spin-valve structures by observing hysteresis, switching field distribution (SFD), and time-dependent effects. The fact that time-dependent coercivity Hc tendency is more pronounced in ordered AF materials than that of disordered AF materials implies a spin reversal of some AF grains with locally low pinning field and low blocking temperature. We propose a simple qualitative model to explain our results in terms of a distribution of the pinning reversal field and temperature in AF layer, which may be due to a grain size distribution in the AF layer and an incomplete and inhomogeneous phase transformation in some ordered AF materials. High resolution electron microscopy (HREM) results reveal that lattice spacing does change from place to place in AF region of some ordered AF materials. The evidence indicates an incomplete and inhomogeneous phase transformation in the ordered AF systems, supporting the results of the magnetization reversal process study. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372503
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  • 3
    Electronic Resource
    Electronic Resource
    Exchange anisotropy and micromagnetic properties of PtMn/NiFe bilayers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6588-6590 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic microstructure, exchange induced uniaxial and unidirectional anisotropy and structural transformation have been studied in PtMn/NiFe bilayer films and small elements as a function of annealing time. The relationship between the fcc-fct ordering phase transformation in PtMn and the development of exchange induced magnetic properties in PtMn/NiFe bilayers is complicated by the fact that the transformation occurs throughout the entire volume of the PtMn film, while the exchange between the layers is predominantly an interface effect. Consequently, the development of the exchange anisotropy should depend primarily on the character of the structural transformation at the interface between PtMn and NiFe. The purpose of this article is to correlate the volume phase transformation in PtMn to the development of exchange anisotropy and micromagnetic behavior in PtMn/NiFe bilayers. The interface structure can be inferred from the anisotropy and micromagnetic measurements, leading to a model that explains the relationship between the volume and interface transformation structures in PtMn, and magnetic properties of the bilayers. The structure and magnetic properties were characterized by x-ray diffraction, vibrating sample magnetometry, and magnetic force microscopy. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1360676
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  • 4
    Electronic Resource
    Electronic Resource
    Improvement of giant magnetoresistance properties of CrMnPt spin valves by dc magnetron sputtering (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6662-6664 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: CrMnPt spin valve films with high a giant magnetoresistance (GMR) ratio of 14% were fabricated using dc magnetron sputtering. The switching field is above 700 Oe and the blocking temperature is 320 °C for a 250 Å CrMnPt pinning layer in a simple top spin valve stack. The exchange interfacial coupling constant is of 0.22 erg/cm2 which is much higher than that of the rf sputtered films. The as-made spin valve shows an abnormal resistance transition below the blocking temperature of 150 °C. The results indicate that the deposition method can influence the GMR properties greatly through the modification of the microstructure. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372803
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  • 5
    Electronic Resource
    Electronic Resource
    Study of exchange anisotropy in NiFe/NiMn and NiFe/IrMn exchange coupled films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4916-4918 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Exchange anisotropy in NiFe/NiMn and NiFe/IrMn exchange coupled films was studied as a function of temperature using vibrating sample magnetometry. The exchange field was measured using three different methods: (1) as a shift of the hysteresis loop measured in an external field applied parallel to the exchange field direction; (2) calculated from the initial susceptibility in the field applied perpendicular to the exchange field; and (3) calculated from the shift of minor reversible hysteresis loops measured in external fields applied in a few different directions close to the perpendicular to the exchange field. The values of the exchange field in NiFe/NiMn samples measured using methods 2 and 3 were similar and approximately twice as high as the values measured using method 1. For the NiFe/IrMn samples methods 2 and 3 gave exchange field values slightly exceeding the values obtained using method 1. The results are explained using a model in which it is assumed that the interfacial interactions between antiferromagnetic and ferromagnetic layers induce unidirectional and uniaxial anisotropy in the ferromagnetic layer. The temperature dependence of induced interfacial uniaxial anisotropy was calculated from the experimental data. For the NiFe/NiMn samples, the temperature dependence of the induced uniaxial anisotropy was significantly different from that of the unidirectional anisotropy. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369141
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  • 6
    Electronic Resource
    Electronic Resource
    Angular dependence of giant magnetoresistance properties of exchange biased spin valves (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5033-5035 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Giant magnetoresistance (GMR) responses were studied as a function of applied measurement field angle in FeMn and NiMn pinned spin valves. As the measurement field varies away from the pinning field direction, the peak GMR ratio and the free layer coercivity decrease. The GMR curve changes from unsymmetrical to symmetrical with respect to the applied field polarity. The GMR responses from the component parallel to the applied field are proportional to the cosine of the angle between the pinning and the applied field. The results can be described well by a simple vector model, and an empirical method to measure the pinning field rotation is established. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370082
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  • 7
    Electronic Resource
    Electronic Resource
    Spin valves with antiparallel-pinned flux compensation layer (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6606-6608 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The reduction of the demagnetization field in the spin-valve sensor was realized by introducing an antiparallel-pinned flux compensation layer built in a bottom spin-valve structure of substrate/Ta/NiFe/IrMn/NiMn/NiFe/Co/Cu/Co/NiFe/Ta. Two antiferromagnetic layers, NiMn and IrMn, were used to pin the pinned and flux compensation layers separately. The magnetization direction of the flux compensation layer was set through a magnetic anneal at a temperature between the blocking temperatures of IrMn and NiMn. The bias field and sensitivity were improved with a reduction of the demagnetization field at the free layer. Furthermore, the free layer coercivity was reduced and a better magnetic stability was achieved. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372785
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic and thermal relaxation in (NiFe/CoFe)/PtMn and NiFe/NiMn bi-layers for spin valve heads (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6424-6426 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic and thermal relaxation of exchange coupling, Hex in (NiFe/CoFe)/PtMn and NiFe/NiMn bi-layers has been studied as a function of temperature between 25 °C to 250 °C and magnetic field between 0 to 1000 Oe applied antiparallel to the original exchange coupling direction. The blocking temperature was about 380 °C for (NiFe/CoFe)/PtMn, and 410 °C for NiFe/NiMn. It was found that the Hex of the bi-layers decreased gradually with increasing time, while the coercivities remained almost a constant. The Hex, measured at a temperature of 250 °C and a reversal field of 1000 Oe, decreased from 205 Oe to 0 and then changed its sign. The relaxation time, defined as the time required for Hex to reach zero, is about 3.1 h and 8.7 h for (NiFe/CoFe)/PtMn and NiFe/NiMn, respectively. The relaxation process for the bi-layers could be understood as the superposition of two exponential decays with different rates associated with a distribution of energy barriers. Spin valve heads using NiFe/NiMn bi-layers could be expected more stable, than those using (NiFe/CoFe)/PtMn bi-layers at an elevated operating temperature. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372726
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  • 9
    Electronic Resource
    Electronic Resource
    Giant magnetoresistance properties of patterned IrMn exchange biased spin valves (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 6112-6114 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Giant magnetoresistance (GMR) responses were studied in micron-sized IrMn pinned spin valve stripes. As the stripe height is decreased both the pinning field and free layer bias field increase while the GMR ratio stays almost constant. The free layer coercivity becomes zero for the shortest stripe while the pinned layer coercivity drops slightly at high aspect ratio. The pinned layer switching field is enhanced in the patterned films, indicating a strong magnetostatic coupling between the free and pinned layer that was further simulated micromagnetically. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370278
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  • 10
    Electronic Resource
    Electronic Resource
    Temperature dependence of giant magnetoresistance properties of NiMn pinned spin valves : 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. 6807-6809 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The giant magnetoresistance response of NiMn pinned spin valves was studied at elevated temperature. Top spin valve films were made by ion beam sputtering and thermally treated to induce the strong unidirectional pinning field in the pinned layer. Both δR and δR/R decrease linearly with temperature. The sheet resistance of the spin valves also increases linearly with temperature. The exchange coupling between pinned layer and free layer decreases slightly and the coercivity of the free layer increases slightly. The temperature dependence of the exchange pinning field is unique in NiMn spin valves. The pinning field has a weakly increasing temperature dependence up to 200 °C, then decreases to zero at the blocking temperature of 380 °C. Samples with different thickness NiMn layers show different temperature dependencies. However, the blocking temperature is unchanged. The pinning fields of NiMn, FeMn, IrMn, and NiO spin valves were also measured up to 200 °C; NiMn pinned spin valves show the least dependence of pinning field at elevated temperatures. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367639
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