Quantitative Decoding of Interactions in Tunable Nanomagnet Arrays Using First Order Reversal Curves

Gilbert, Dustin A.; Zimányi, Gergely T.; Dumas, Randy K.; Winklhofer, Michael; Gómez, A.; Eibagi, Nasim; Vicent, J. L.; Liu, Kai

doi:10.1038/srep04204

Cited by 136 publications

(138 citation statements)

References 35 publications

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“…In the investigation of nanomagnet assemblies, the focus has mainly been on lithographicallypatterned, planar structures, which can be used as logic devices capable of executing Boolean logic operations [1][2][3][4][5][6][7][8]. Often applications are sought within high density recording, bit patterned media [9][10][11][12] or MRAM devices [1,13], however since the bit size of modern hard disk drives (approx.…”

Section: Introductionmentioning

confidence: 99%

Intra-wire coupling in segmented Ni/Cu nanowires deposited by electrodeposition

Sergelius¹,

Lee²,

Fruchart³

et al. 2017

Nanotechnology

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Segmented magnetic nanowires are a promising route for the development of three dimensional data storage techniques. Such devices require a control of the coercive field and the coupling mechanisms between individual magnetic elements. In our study, we investigate electrodeposited nanomagnets within host templates using vibrating sample magnetometry and observe a strong dependence between nanowire length and coercive field (25 nm to 5 µm) and diameter (25 nm to 45 nm). A transition from a magnetization reversal through coherent rotation to domain wall propagation is observed at an aspect ratio of approximately 2. Our results are further reinforced via micromagnetic simulations and angle dependent hysteresis loops. The found behavior is exploited to create nanowires consisting of a fixed and a free segment in a spin-valve like structure. The wires are released from the membrane and electrically contacted, displaying a giant magnetoresistance effect that is attributed to individual switching of the coupled nanomagnets. We develop a simple analytical model to describe the observed switching phenomena and to predict stable and unstable regimes in coupled nanomagnets of certain geometries.-2 - INTRODUCTIONIn the investigation of nanomagnet assemblies, the focus has mainly been on lithographicallypatterned, planar structures, which can be used as logic devices capable of executing Boolean logic operations [1][2][3][4][5][6][7][8]. Often applications are sought within high density recording, bit patterned media [9][10][11][12] or MRAM devices [1,13], however since the bit size of modern hard disk drives (approx. 20x20 nm²) is already lower than what is achievable with most lithography techniques [14], potential use is limited. Therefore, the use of the third dimension is an appealing approach. Studies on alternating, vertical stacks of magnetic and non-magnetic materials have already been published, in which a three dimensional shift register is investigated, that is capable of storing and shifting several bits of information as solitons within a single column [15][16][17][18][19]. These shift registers are coupled via RKKY interaction and its oscillatory nature allows for an additional degree of freedom in the design of the device, but as a drawback the samples are very demanding with regard to sample quality and purity. A soliton, which is the bearer of information, is a magnetic frustration within a 1D chain of magnetic moments. It is thinkable to induce such a soliton using dipolar coupling instead of RKKY, simply by magnetizing two nanomagnets in the same direction and placing them next to each other (transversal soliton [20]). Another possibility would be to magnetize them in opposing direction and place them in a head-to-head or tail-to-tail configuration (longitudinal soliton, Figure 1). The coupling strength is then defined by the material properties and the distance of both nanomagnets. Such kinds of nanowires can be synthesized within porous anodic aluminum oxide (AAO) templates [21-23] using electro...

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Section: Introductionmentioning

confidence: 99%

Intra-wire coupling in segmented Ni/Cu nanowires deposited by electrodeposition

Sergelius¹,

Lee²,

Fruchart³

et al. 2017

Nanotechnology

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“…The emergence of 2 "ridges" actually indicates there exists 2 kinds of interactions in our sample, the major "ridge" reflects the influence of exchange coupling interaction while the other one reflects magneto-static interaction. 6,8 In order to get more detailed information of FORC diagrams, we calculate series of parameters according to the FORC data. Table I is our computation results of ECC films along with 5nm-thick and 11nm-thick FePt films, and FePt/[Co/Ni] N (N = 3, 5, 10) ECC composite.…”

Section: Methodsmentioning

confidence: 99%

“…FORC is a useful tool to study the magnetic interaction between grains. 8 In this paper, we report the angular variation magnetic study of the ECC L1 0 -FePt/[Co/Ni] N multilayers to investigate the magnetic reversal mechanism. Then we employ FORC analysis and give a comprehensive description of the interactions existing in our films by calculating series of FORC parameters.…”

Section: Introductionmentioning

confidence: 99%

FORC-study of magnetization reversal of L1-FePt based exchange coupled composite films

Situ

Wang

2017

AIP Advances

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Perpendicular exchange coupled composite structures were prepared, utilizing L10-FePt as hard layer and [Co/Ni]N multilayer as soft layer. Magnetic characteristics revealed the gradually change of the magnetization reversal mechanism from incoherent rotational mode to dominant wall motion as the thickness of soft layer increases. Furthermore, FORC analysis were employed to characterize the interactions of our ECC magnetic system, the result indicates that the exchange coupling interaction were enhanced with the increasing thickness of soft layer.

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“…The concentric distribution at high coercivity suggests single domain (SD) particles, 25,26 and the large vertical spread of the high coercivity component suggests the interaction between these SD particles. 1,27 The bias to negative interaction (H u ) suggests mean field magnetizing interactions, 28 which would be expected from packed hexagonal plate 21 crystals. The distribution of low coercivity component also showed spread along the H u axis, but the spread gradually decreases with increasing coercivity, which suggests pseudo-single domain (PSD) particles.…”

Section: Micro Samplementioning

confidence: 99%

Multiphase magnetic systems: Measurement and simulation

Cao

Ahmadzadeh

et al. 2018

Journal of Applied Physics

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Multiphase magnetic systems are common in nature and are increasingly being recognized in technical applications. One characterization method which has shown great promise for determining separate and collective effects of multiphase magnetic systems is first order reversal curves (FORCs). Several examples are given of FORC patterns which provide distinguishing evidence of multiple phases. In parallel, a visualization method for understanding multiphase magnetic interaction is given, which allocates Preisach magnetic elements as an input 'Preisach hysteron distribution pattern' (PHDP) to enable simulation of different 'wasp-waisted' magnetic behaviors. These simulated systems allow reproduction of different major hysteresis loop, FORC pattern, and switching field distributions of real systems and parameterized theoretical systems.The experimental FORC measurements and FORC diagrams of four commercially obtained magnetic materials, particularly those sold as nanopowders, shows that these materials are often not phase pure. They exhibit complex hysteresis behaviors that are not predictable based on relative phase fraction obtained by characterization methods such as diffraction. These multiphase materials, Even though the ideal characteristics of hysteresis in perfect single magnetic domains is generally accepted, it is still a challenge to interpret the hysteresis of real materials, as it depends on particle size, shape, and distribution, as well as stress, defects, and impurities. The hysteresis of magnetic mixtures is even more complex, as interactions between non-dilute phases distort the simple loop shape. However, the parameters extracted from major hysteresis loop -for instance, coercivityare not very efficient at showing the interactions of magnetic phases in a multiphase system. First order reversal curve (FORC) analysis is one technique which has developed rapidly in the last two decades, 1 providing a powerful tool for observing magnetic switching contributed by different magnetic phases. FORC is now applied to understand various hysteretic behaviors in metalinsulator transitions, 2 ferroelectricity, 3 magnetocalorics, 4 and perpendicular magnetic recording media. 5 The FORC technique can also be employed to distinguish the different magnetic signals in multiphase systems 4,6 to investigate subtle magnetic features caused by interaction of multiple magnetic phases.In this paper, a series of multiphase magnetic nanopowders are investigated experimentally using major hysteresis loops and FORC diagrams and these systems are also modeled using 'Preisach hysteron distribution patterns' (PHDPs) based on the classical Preisach model (CPM) to aid in descriptive understanding of the reduction of coercivity, or 'wasp-waistedness' features, observed in major loops of multiphase materials. The FORC diagrams of them generally indicate the existence of a low coercivity phase, a high coercivity phase, and a coupling region, which can all be simulated using PHDPs. Together, the simulations and measurements pr...

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Quantitative Decoding of Interactions in Tunable Nanomagnet Arrays Using First Order Reversal Curves

Cited by 136 publications

References 35 publications

Intra-wire coupling in segmented Ni/Cu nanowires deposited by electrodeposition

Intra-wire coupling in segmented Ni/Cu nanowires deposited by electrodeposition

FORC-study of magnetization reversal of L1-FePt based exchange coupled composite films

Multiphase magnetic systems: Measurement and simulation

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