Structure and magnetization in CoPd thin films and nanocontacts

Morgan, Caitlin; Schmalbuch, K.; García‐Sánchez, Felipe; Schneider, Claus M.; Meyer, Carola

doi:10.1016/j.jmmm.2012.07.052

Cited by 6 publications

(11 citation statements)

References 25 publications

(12 reference statements)

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“…The observed temperaturedependent change in width of the MR signal corresponds to a changing difference in coercive fields of the contacts. This behavior, in turn, correlates well with temperaturedependent SQUID data of CoPd [22], which shows that at 50 K, magnetoelastic anisotropy strongly affects the magnetization of nanocontact arrays, resulting in a lowered coercive field. This effect is different for the two contacts because of the interplay of shape anisotropy and magnetoelastic anisotropy.…”

Section: Resultssupporting

confidence: 80%

“…This effect is different for the two contacts because of the interplay of shape anisotropy and magnetoelastic anisotropy. The reduced magnitude of the MR signal at elevated temperatures cannot be attributed to a decrease in magnetization of the CoPd contacts since their saturation magnetization is constant within this temperature range [22]. Therefore, this is a first indication that the MR effect is due to tunneling and we refer to it as TMR (tunneling magnetoresistance) in the following.…”

Section: Resultsmentioning

confidence: 97%

“…The distance between the CoPd contacts is 150 nm and the width of the contacts is 150 nm and 400 nm respectively, which in turn leads to different aspect ratios for the two contacts and in consequence to different coercive fields due to shape anisotropy. A non-trivial temperature dependence of the coercive field has been found and attributed to the interplay of the shape anisotropy and the magnetoelastic effect [22]. The influence of this effect on the switching in magnetoresistance measurements is analyzed and discussed below (see Sec.…”

Section: Methodsmentioning

confidence: 99%

“…Importantly, pinning and moving of domain walls in contacts that incorporate several magnetic domains leads to unstable switching behavior of the contacts and a non-trivial MR signal [26]. For this reason, we optimized the shape of the contacts in such a way that the magnetization is in-plane along the long axis with a single or at most two domains [22]. The magnetic field in all magnetoresistance measurements presented in this work is applied in direction of the long axis of the contacts unless specified otherwise.…”

Section: Methodsmentioning

confidence: 99%

“…The sample is then rotated at zero applied field. Subsequently, a magnetic field is applied perpendicular to the plane, which leaves the magnetization of the contacts unaffected due to the shape anisotropy [22]. The resulting Hanle signal is presented in Fig.…”

Section: Spin Precession Within Carbon Nanotubesmentioning

confidence: 99%

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Impact of Tunnel-Barrier Strength on Magnetoresistance in Carbon Nanotubes

et al. 2016

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We investigate magnetoresistance in spin valves involving CoPd-contacted carbon nanotubes. Both temperature and bias voltage dependence clearly indicate tunneling magnetoresistance as the origin. We show that this effect is significantly affected by the tunnel barrier strength, which appears to be one reason for the variation between devices previously detected in similar structures. Modeling the data by means of the scattering matrix approach, we find a non-trivial dependence of the magnetoresistance on the barrier strength. Furthermore, analysis of the spin precession observed in a nonlocal Hanle measurement yields a spin lifetime of τs = 1.1 ns, a value comparable with those found in silicon-or graphene-based spin valve devices.

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Spin Precession Within Carbon Nanotubesmentioning

confidence: 99%

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Impact of Tunnel-Barrier Strength on Magnetoresistance in Carbon Nanotubes

et al. 2016

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Effect of contact geometry on magnetoresistance in CoPd-contacted carbon nanotubes

Morgan

Metten

Schneider

et al. 2013

Phys. Status Solidi B

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We present local magnetoresistance measurements on carbon nanotubes contacted with the ferromagnetic alloy Co50 Pd50. A sample with contacts of dimensions thickness=10nm, normallength=4thinmathspaceμm exhibited the typical sharp switching expected at the coercive fields of the contacts. However, a sample with the same in‐plane geometry but a thickness of 40 nm displayed a complicated switching behavior indicative of gradual domain wall rotation. In both samples, the contact widths were varied to control shape anisotropy. Further characterization of the contacts and similar contact‐like structures via remanent state magnetic force microscopy suggested a single or few domain structure in the 10 nm thick contacts. The thicker contacts exhibited a complex domain structure characteristic of a hard or intermediate magnetic axis along the long axis of the contact, despite the effect of shape anisotropy. This result is discussed with respect to the influence of both thickness and in‐plane geometry on competing anisotropy contributions within the device. The characterization allows for the pinpointing of precise dimensions that will determine the magnetic easy axis of contacts, thereby controlling magnetotransport.

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