Magnetization reversal in elongated Fe nanoparticles

Li, Yongqing; Xiong, Peng; Molnár, S. von; Ohno, Y.; Ohno, Hideo

doi:10.1103/physrevb.71.214425

Cited by 19 publications

(16 citation statements)

References 29 publications

(50 reference statements)

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“…13 However, even in SD nanoparticles, the magnetization reversal can be quite complex, involving thermally activated incoherent processes. 14 The VS-SD crossover itself is fascinating. For example, recently Jausovec et al have proposed that a third, metastable, state exists in 97 nm permalloy nanodots, based on minor loop and remanence curve studies.…”

Section: Introductionmentioning

confidence: 99%

Magnetic fingerprints of sub-100nmFe dots

et al. 2007

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Sub-100 nm nanomagnets not only are technologically important, but also exhibit complex magnetization reversal behaviors as their dimensions are comparable to typical magnetic domain wall widths. Here we capture magnetic "fingerprints" of 10 9 Fe nanodots as they undergo a single domain to vortex state transition, using a first-order reversal curve ͑FORC͒ method. As the nanodot size increases from 52 nm to 67 nm, the FORC diagrams reveal striking differences, despite only subtle changes in their major hysteresis loops. The 52 nm nanodots exhibit single domain behavior and the coercivity distribution extracted from the FORC distribution agrees well with a calculation based on the measured nanodot size distribution. The 58 and 67 nm nanodots exhibit vortex states, where the nucleation and annihilation of the vortices are manifested as butterflylike features in the FORC distribution and confirmed by micromagnetic simulations. Furthermore, the FORC method gives quantitative measures of the magnetic phase fractions, and vortex nucleation and annihilation fields.

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Section: Introductionmentioning

confidence: 99%

Magnetic fingerprints of sub-100nmFe dots

et al. 2007

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“…Recent studies have shown that near the SD-VS phase boundary, both phases can be stabilized and conversion from one to the other can be triggered by thermal activation or magnetic field cycling. 8,10 Therefore, it is not always reliable to use the nanomagnet remanent magnetic configuration or the shape of the hysteresis loop to determine the presence of VS. 14 On the other hand, the irreversible events associated with vortex nucleation and annihilation are clear signatures of VS. They can be used to track the nanomagnets that reverse via VS, regardless whether the remanent state is VS or not.…”

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confidence: 99%

“…There have been extensive theoretical and experimental studies on SD-VS phase diagrams as a function of nanomagnet dimensions. 6,[8][9][10] Typically, e.g., in isotropic circular dots, the VS evolution from positive saturation starts with an abrupt magnetization drop at a positive nucleation field, followed by a flux closure state with zero remanence and finally the vortex annihilation at a negative field. 6 Observation of the VS at remanence using magnetic microscopy 5 has indeed become a common practice.…”

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confidence: 99%

Temperature induced single domain–vortex state transition in sub-100nm Fe nanodots

Dumas

Liu

et al. 2007

Applied Physics Letters

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Magnetization reversal in nanomagnets via a vortex state, although often investigated at the remanent state, may not necessarily display a zero remanence or a highly pinched hysteresis loop. In contrast, the irreversible nucleation/annihilation events are clear indications of a vortex state. In this work, temperature induced single domain–vortex state transition has been investigated in 67nm Fe nanodots using a first-order reversal curve (FORC) technique. The two phase coexistence is manifested as different features in the FORC distribution. At lower temperatures, it becomes harder to nucleate and annihilate vortices and the amount of single domain dots increases.

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“…These measurements have been carried out in a gradiometry setup where the Hall voltage at the cross carrying the sample is compensated by applying a current of same magnitude but opposite sign through an empty reference cross. This results in a differential signal ∆V H solely due to the sample's magnetization [9,10]. The data in since for multiple walls the magnetization reversal wouldn't be expected to follow only a few distinct paths.…”

Section: Resultsmentioning

confidence: 99%

Domain wall dynamics in a single CrO₂grain

Das

Porrati

Wirth

et al. 2011

J. Phys.: Conf. Ser.

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Abstract. Recently we have reported on the magnetization dynamics of a single CrO2 grain studied by micro Hall magnetometry (P. Das et al., Appl. Phys. Lett. 97 042507, 2010). For the external magnetic field applied along the grain's easy magnetization direction, the magnetization reversal takes place through a series of Barkhausen jumps. Supported by micromagnetic simulations, the ground state of the grain was found to correspond to a flux closure configuration with a single cross-tie domain wall. Here, we report an analysis of the Barkhausen jumps, which were observed in the hysteresis loops for the external field applied along both the easy and hard magnetization directions. We find that the magnetization reversal takes place through only a view configuration paths in the free-energy landscape, pointing to a high purity of the sample. The distinctly different statistics of the Barkhausen jumps for the two field directions is discussed. IntroductionIn the realm of magnetism, the concept of domains and domain walls (DWs) are at the core of the understanding of the spontaneous magnetization of a ferromagnetic material. The domains, which are formed as a result of minimization of the total free energy, undergo structural changes under the influence of an external field. In real materials, the structural or compositional imperfections lead to several minima in the free energy landscape. These imperfections act as pinning centers for the DWs. An understanding of the dynamics of DWs in the presence of pinning centers is critical for the understanding of parameters like coercivity and remanence, which is essential for improving materials for practical applications. However, this is often difficult to realize in real samples consisting of several domains and DWs, where one measures an average magnetic signal and the details of the configuration path followed by the various DWs (due to local effects of pinning centers) are averaged out. Therefore, in order to gain detailed and quantitative information on the magnetization processes, as e.g. the pinning center distribution in a sample, it is essential to investigate samples where a single DW is present.In literature, several studies on the dynamics of a single DW have been reported where, in most cases, a single wall is artificially created [1,2,3]. In the present study, we explore the possibilities of quantitative investigation of the dynamics of a single DW in an individual CrO 2 micro-grain of dimensions of approximately 5 × 1.2 × 0.7 µm 3 . The DW in the present case is not

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Magnetization reversal in elongated Fe nanoparticles

Cited by 19 publications

References 29 publications

Magnetic fingerprints of sub-100nmFe dots

Magnetic fingerprints of sub-100nmFe dots

Temperature induced single domain–vortex state transition in sub-100nm Fe nanodots

Domain wall dynamics in a single CrO₂grain

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Magnetization reversal in elongated Fe nanoparticles

Cited by 19 publications

References 29 publications

Magnetic fingerprints of sub-100nmFe dots

Magnetic fingerprints of sub-100nmFe dots

Temperature induced single domain–vortex state transition in sub-100nm Fe nanodots

Domain wall dynamics in a single CrO2grain

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Domain wall dynamics in a single CrO₂grain