Radially Anisotropic Toroidal Magnetic Core Fabrication

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Solution Overview

Problem

Thin-film magnetic materials exhibit strong anisotropy, making them difficult to use in toroidal geometries due to directional dependence of magnetic properties, which leads to challenges in power conversion applications where external magnetic fields can cause interference and losses.

Innovation Solution

A method of fabricating a radially anisotropic toroidal magnetic core by depositing ferromagnetic materials in a radial magnetic field, aligning the easy axis radially and the hard axis circumferentially to minimize perpendicular anisotropy and promote low hysteretic losses and high inductance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If thin-film magnetic materials are used in toroidal geometries, then power conversion applications benefit from reduced eddy current losses and minimal external magnetic fields, but the strong anisotropy of the materials makes them difficult to use due to directional dependence of magnetic properties

Engineering Contradiction:

Improveeddy current lossesVSAvoiddifficulty to use in toroidal geometries

Core Design Contradiction:

Loss of energyVSEase of manufacture

Solution Approach 1:

The patent applies local quality by creating radially varying magnetic properties within the toroidal core. The easy axis of magnetization is oriented radially at each point in the core, allowing the magnetic properties to be optimized for the local flux direction while maintaining toroidal geometry. This radial orientation of anisotropy enables the core to efficiently guide magnetic flux around the torus without the directional limitations that would otherwise prevent use in toroidal configurations

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the magnetic anisotropy parameter from conventional planar orientation to radial orientation throughout the toroidal structure. By modifying the easy axis direction to follow the radial geometry of the torus, the material's magnetic properties are adapted to match the required flux path, enabling effective use in toroidal geometries while maintaining the energy loss benefits of this configuration

Inventive Principle:

Principle #35Parameter changes

2Reliability

If conventional anisotropic thin-film materials are used, then magnetic properties are optimized for a specific direction, but external magnetic fields cause electromagnetic interference and induced eddy-currents leading to power losses

Engineering Contradiction:

Improvemagnetic property optimizationVSAvoidelectromagnetic interference and eddy-current losses

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent employs asymmetry by creating a radially symmetric toroidal structure with locally optimized magnetic properties that break the conventional planar symmetry. The radial orientation of magnetic anisotropy creates an asymmetric magnetic circuit that confines flux within the core material, reducing external field leakage and the associated electromagnetic interference and eddy-current losses in surrounding conductors

Inventive Principle:

Principle #4Asymmetry

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The radially anisotropic cores demonstrate improved performance with flat relative permeability and high quality factors, suitable for high-frequency inductors and transformers by minimizing external magnetic field interference and eddy current losses.

Implementation Method 1

depositing ferromagnetic materials in a radial magnetic field, aligning the easy axis radially and the hard axis circumferentially

Methodology Applied

Scientific EffectMagnetic field alignment: Magnetic Field

Implementation Method 2

Thin-film magnetic materials exhibit strong anisotropy—a property whereby the materials are easier to magnetize along one axis, the easy axis, than in another, or hard, axis

Methodology Applied

Scientific EffectMagnetic anisotropy: Anisotropy

Implementation Method 3

depositing ferromagnetic materials in a radial magnetic field

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS9659706B2Methods for making radially anisotropic thin-film magnetic torroidal cores

Publication Date: 2017.05.23 TRUSTEES OF DARTMOUTH COLLEGE THE

AI summary

A method of forming a radially anisotropic toroidal magnetic core includes providing apparatus having a first magnet for providing a radial magnetic field extending across a cavity from an axial spindle to a surrounding second magnetic element, placing a substrate in the cavity, the substrate having a hole fitting around the head of the spindle; and sputter-depositing a film of ferromagnetic material onto the substrate. In an embodiment, the spindle is magnetically coupled to a first pole of the first magnet, the second magnetic element is coupled to a second pole of the first magnet, and a thermally conductive, nonmagnetic, insert separates the spindle and the second magnetic element.