Three-dimensional dynamics of a particle with a finite energy of magnetic anisotropy in a rotating magnetic field.

Abstract

A model of a single ferromagnetic particle with a finite coupling energy of the magnetic moment with the body of the particle is formulated, and regimes of its motion in a rotating magnetic field are investigated. Regimes are possible that are synchronous and asynchronous with the field. In a synchronous regime the easy axis of the particle is in the plane of the rotating magnetic field at low frequencies (a planar regime) and on the cone at high frequencies (a precession regime). The stability of these regimes is investigated, and it is shown that the precession regime is stable for field strengths below the critical value. In a particular range of field strength value, irreversible jumps of the magnetic moment take place in the asynchronous planar regime. The stability of this regime is investigated, and it is shown that it is stable for field strengths above the critical value, which depends on the frequency. The implications of these results for the energy dissipation in a rotating field are analyzed, and it is shown that the maximum of the heat production near the transition to the synchronous regime is flattened out by the transition to the precession regime.

AI evidence extraction

Main findings

A theoretical model of a single ferromagnetic particle in a rotating magnetic field predicts synchronous and asynchronous motion regimes. The synchronous regime is planar at low frequencies and becomes a stable precession regime at high frequencies for field strengths below a critical value; in a range of field strengths, irreversible magnetic-moment jumps occur in an asynchronous planar regime that is stable above a frequency-dependent critical field. The analysis suggests the heat-production maximum near transition to the synchronous regime is flattened by transition to the precession regime.

Outcomes measured

• particle motion regimes (synchronous/asynchronous)
• stability of planar and precession regimes
• irreversible jumps of magnetic moment
• energy dissipation / heat production in rotating field

Limitations

• No biological/health outcomes assessed (physics model of a single ferromagnetic particle).
• No specific field parameters (e.g., frequency values, field strength units) provided in the abstract.
• Model-based results; experimental validation not described in the abstract.

{
    "study_type": "other",
    "exposure": {
        "band": null,
        "source": "rotating magnetic field",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": null,
    "sample_size": null,
    "outcomes": [
        "particle motion regimes (synchronous/asynchronous)",
        "stability of planar and precession regimes",
        "irreversible jumps of magnetic moment",
        "energy dissipation / heat production in rotating field"
    ],
    "main_findings": "A theoretical model of a single ferromagnetic particle in a rotating magnetic field predicts synchronous and asynchronous motion regimes. The synchronous regime is planar at low frequencies and becomes a stable precession regime at high frequencies for field strengths below a critical value; in a range of field strengths, irreversible magnetic-moment jumps occur in an asynchronous planar regime that is stable above a frequency-dependent critical field. The analysis suggests the heat-production maximum near transition to the synchronous regime is flattened by transition to the precession regime.",
    "effect_direction": "unclear",
    "limitations": [
        "No biological/health outcomes assessed (physics model of a single ferromagnetic particle).",
        "No specific field parameters (e.g., frequency values, field strength units) provided in the abstract.",
        "Model-based results; experimental validation not described in the abstract."
    ],
    "evidence_strength": "insufficient",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "rotating magnetic field",
        "ferromagnetic particle",
        "magnetic anisotropy",
        "synchronous regime",
        "asynchronous regime",
        "precession",
        "stability",
        "energy dissipation",
        "heat production"
    ],
    "suggested_hubs": []
}

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