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  • 1
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance of molecular beam epitaxially grown Co-Cu superlattices that exhibit large magnetoresistance : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6381-6383 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The 59Co NMR has been measured for superlattices of Co(15 A(ring))/Cu (7 or 18 A(ring)) grown with either a Au or Cu buffer layer between the substrate and the superlattice. As was reported earlier the Co (15 A(ring))/Cu (7 A(ring)) (Au) superlattice has the largest magnetoresistance (ΔR/R∼26%) known for a MBE grown Co/Cu multilayer. The NMR measurements show that the Au-based superlattices have very flat interfaces and (111) orientation, two features which were supposed to preclude a large value of ΔR/R, and that the average strain in the Co layers is greater for a Au than a Cu buffer layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352657
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  • 2
    Electronic Resource
    Electronic Resource
    59Co nuclear magnetic resonance studies of the effect of annealing molecular beam epitaxy grown Co/Cu(111) multilayers : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5119-5121 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 59Co NMR, magnetotransport and grazing incidence x-ray scattering studies have been undertaken on a series of Co/Cu(111) multilayers, grown by molecular beam epitaxy (MBE), and subsequently annealed. Magnetotransport measurements showed that the magnetoresistance (Δρ/ρ) decreased only slightly as the annealing temperature was increased, but both the resistivity ρ and the change in resistivity Δρ doubled. NMR measurements showed that the strain in the interior of the Co layers relaxed slightly as a result of annealing while the strain at the interfaces remained constant. A small increase in the ratio of the area under the main NMR line to the area under the interface line, together with a reduction of interface line area, suggests a slight deterioration in the quality of the interfaces as a result of annealing. These observations are consistent with the model that MBE grown multilayers require good quality interfaces for large magnetoresistance (MR). Data from x-ray measurements showed that the increase in resistivity could be explained as a result of alloying between the top Cu layer of the multilayer and the Au capping layer. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361321
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  • 3
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance study of expanded lattice permanent magnet nitrides and carbides at high pressure : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4599-4601 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nuclear magnetic resonance spin-echo spectra of 89Y and 147Sm for Y2Fe17, Y2Fe17C0.4, Y2Fe17C1.5, Y2Fe17N2.5, Y2Fe17CN1.5, Y2Fe17H1.6, and Sm2Fe17 have been measured at pressures up to 10 kbar at 4.2 K. A reduction of the magnitude of the valence electron polarization contribution to the effective field Be at Y and Sm sites with pressure is observed. The effect is strongly related to the nearest neighbor environment of the site. A significant reduction of ∂B/∂p is observed for the sites with nitrogen neighbors. Carbon increases (decreases) ∂B/∂p in the rhombohedral (hexagonal) structure of the compound. A decrease of the lattice electric field gradient at the Sm site in Sm2Fe17 with pressure is observed. A corresponding decrease of the crystal electric field coefficient A02 at the Sm site with pressure of 0.7% per kbar is derived, indicating an anisotropic compressibility of the material. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361863
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  • 4
    Electronic Resource
    Electronic Resource
    59Co and 55Mn NMR of CoMn alloys and multilayers : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6300-6302 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 59Co and 55Mn NMR measurements have been made on a range of CoMn materials: dilute powder alloy, thin-film alloys, and multilayers. Our results suggest that in dilute alloys isolated atoms of Mn couple both ferro and antiferromagnetically to the Co host, with the latter producing a reduction in the magnitude of the Co hyperfine field of 17%. This reduction of hyperfine field appears similar for both the fcc and hcp phases of Co. NMR on Co/Mn sputtered multilayers shows large changes in the hyperfine field distribution between a film with Mn layers of 10 A(ring) and Mn layers of 30 A(ring). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362044
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic properties of (Pr(Ca, Sr))MnO3 studied by nuclear magnetic resonance : 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. 7151-7153 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The valence state of Mn in magnetoresistive perovskites has been widely related to the level of alkaline metal substitution of the rare earth, by assuming that the Mn exists in 3+ or 4+ valence states. Measurements have been made on a series of samples in the system Pr1−(x+y)CaxSryMnO3. 55Mn nuclear magnetic resonance (NMR) zero field spin echo measurements on a single crystal with x=0.1 and y=0 show distinct resonances around 310 MHz (Mn4+) and 400 MHz (Mn3+) but also at 590 MHz (Mn2+). An increase in the Mn2+ resonance frequency in an applied field implies that the Mn2+ moment is antiferromagnetically coupled to the net magnetization. Spectra from powder samples are much broader. The resonance frequencies increase as the Pr content is reduced. For systems with x+y=0.4, there is little change in the NMR spectrum as the proportions of Ca and Sr are altered. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367626
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  • 6
    Electronic Resource
    Electronic Resource
    Field dependence of nuclear magnetic resonance in molecular beam epitaxy grown Co(111)/Cu multilayers : 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. 6504-6506 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An initial study of the field dependence of 59Co nuclear magnetic resonance (NMR) has been undertaken for two Co/Cu(111) multilayer films grown by molecular beam epitaxy. The multilayer structure of the films was nominally identical, [Co(15 A(ring))/Cu(7 A(ring))]×20, however by growing the multilayers with similar structures on different buffer layers, Cu(200 A(ring)) and Au(10 A(ring)), saturation magnetoresistances ΔR/R of 4% and 22%, respectively, were obtained. The NMR signal in ferromagnetic materials arises due to the enhancement effect from the electronic magnetization. This enhancement effect is therefore a function of the domain structure and any external magnetic field. By applying a simple model of how the NMR enhancement factor varies with applied field, in the absence of a domain structure, the anisotropy fields at the interfaces and in the bulk were determined separately at T=4.2 K. These were then compared with the coercive field obtained from magnetization measurements. Our results show that at low temperature the anisotropy field at the interfaces is approximately equal to the coercivity obtained from magnetization measurements (260 Oe), while in the bulk the anisotropy field was found to be ∼550 Oe for the low magnetoresistance sample with ΔR/R=4%, and ∼1230 Oe for the high magnetoresistance sample with ΔR/R=22%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358243
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  • 7
    Electronic Resource
    Electronic Resource
    Forced magnetostriction and pressure dependence of the magnetism of weakly ferromagnetic Y(Co1−xAlx)2 and Sc3In : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5680-5682 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Curie point and spontaneous magnetization of weakly ferromagnetic Y(Co1−xAlx)2 alloys with x∼0.15 is shown to decrease rapidly with increasing pressure, in agreement with the theory of weak itinerant ferromagnetism. Forced magnetostriction measurements on Sc3In, however, confirm that the magnetization at 4.2 K in a field of ∼2 T increases with pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347936
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  • 8
    Electronic Resource
    Electronic Resource
    Quasi-optical cw mm-wave electron spin resonance spectrometer (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3924-3937 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a novel cw millimeter-wave electron spin resonance (ESR) spectrometer designed to operate in the frequency range of 80–200 GHz and in the temperature range of 2.5–300 K, which may be easily scaled to higher frequencies. The spectrometer uses a bimodal reflection cavity coupled to a circular corrugated guide and uses Gaussian quasi-optics for most of the front-end signal processing. This technique has very low insertion loss and allows a number of sophisticated measurement techniques to be employed including induction operation, which significantly reduces the effect of microphonics and stray reflections. A number of examples are given illustrating the sensitivity of the instrument and the advantages of using ESR at high fields. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149200
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  • 9
    Electronic Resource
    Electronic Resource
    59Co nuclear magnetic resonance study of molecular-beam epitaxy grown Co/V multilayers (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6594-6596 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 59Co nuclear magnetic resonance (NMR) measurements have been undertaken to determine the local atomic environment of Co in Co/V multilayers, previously studied by magnetometry. These NMR measurements provide confirmation, on a local atomic scale, of the results deduced from the earlier magnetization study. Co/V multilayers show considerable interfacial mixing with a magnetically dead, vanadium rich layer penetrating approximately 2 Å into an adjoining Co layer. The presence of this dead layer has the effect of modifying the hyperfine field experienced by the Co nuclei at a distance of several atomic planes from the interface. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372781
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  • 10
    Electronic Resource
    Electronic Resource
    High field ferromagnetic resonance measurements of the anisotropy field of longitudinal recording thin-film media (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1417-1422 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The average value of the magnetocrystalline anisotropy field, Hk, is an important parameter for the characterization of magnetic recording media but is difficult to measure accurately due in part to the effect of interactions between the grains. In order to evaluate Hk we have studied two model CoCrPtTa magnetic films using a number of complementary techniques: high field ferromagnetic resonance (FMR) (35.0–45.0 kOe), low field (〈20 kOe) vector vibrating-sample magnetometry and torque magnetometry. The FMR measurements were performed at a number of discrete frequencies in the range 75–93 GHz using a new quasi-optical spectrometer developed at the University of St. Andrews. The values of Hk derived by FMR (10.8 kOe) are approximately 10% greater than those obtained from conventional magnetometry (9.6 kOe). This difference is believed to be due to the presence of intergranular exchange coupling which reduces the measured value of anisotropy when the applied field is not sufficiently large to completely align the magnetic moments. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428804
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