Systems and methods for measuring local magnetic susceptibility including one or more balancing elements with a magnetic core and a coil
AssigneePhilip Morris USA Inc.
InventorsKudumboor V. Rao, Valter Ström, Ziyan Gu, Seetharama C. Deevi
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Abstract
A local magnetic susceptibility unit is adapted to measure the AC magnetic susceptibility of a surface region of a sample. The unit comprises a sensing element and one or more balancing elements arranged in a circuit. When a sample is placed proximate to the sensing element the sample induces an imbalance voltage in the circuit.
Claims24
A local magnetic susceptibility unit for measuring the AC magnetic susceptibility of a surface region of a sample, comprising:
- a sensing element;
- and
- one or more balancing elements arranged in a circuit, wherein the sensing element comprises:
- a magnetic core having a leading arm;
- a trailing arm with a gap formed therebetween;
- and
- at least one coil wound around the magnetic core and operative to generate, upon connection to a power source, a magnetic field across the gap and to induce an imbalance voltage therein in response to an interaction between the magnetic field and a surface region of a sample,
- wherein the imbalance voltage is measured to determine a magnetic susceptibility of the surface region,
- wherein the sensing element is mounted on a stage to perform a motion of the sensing element with respect to the sample, the motion including translation and rotation.
A local magnetic susceptibility unit for measuring the AC magnetic susceptibility of a surface region of a sample, comprising:
- a sensing element:
- one or more balancing elements arranged in a circuit, wherein the sensing element comprises:
- a magnetic core having a leading arm;
- a trailing arm with a gap formed therebetween;
- and
- at least one coil wound around the magnetic core and operative to generate, upon connection to a power source, a magnetic field across the gap and to induce an imbalance voltage therein in response to an interaction between the magnetic field and a surface region of a sample,
- wherein the imbalance voltage is measured to determine a magnetic susceptibility of the surface region;
- and
- a computer system coupled to the power source, a motor for positioning the sensing element, a temperature controller for controlling a temperature of sample, and a lock-in amplifier and adapted to control at least one of the group consisting of
- a power input to a circuit, a position of the sensing element,
- a temperature of the sample,
- acquisition of AC magnetic susceptibility data, and processing of the data.
A local magnetic susceptibility unit for measuring the AC magnetic susceptibility of a surface region of a sample, comprising:
- a sensing element;
- one or more balancing elements arranged in a circuit, wherein the sensing element comprises:
- a magnetic core having a leading arm;
- a trailing arm with a gap formed therebetween;
- and
- at least one coil wound around the magnetic core and operative to generate, upon connection to a power source, a magnetic field across the gap and to induce an imbalance voltage therein in response to an interaction between the magnetic field and a surface region of a sample,
- wherein the imbalance voltage is measured to determine a magnetic susceptibility of the surface region,
- wherein the unit comprises three balancing elements and the sensing element configured in a bridge circuit, each element comprising a single coil or a pair of coils connected in series via a center tap.
A method of measuring the in-plane AC magnetic susceptibility of a surface region of a sample using a local magnetic susceptibility unit comprising a sensing element, one or more balancing elements arranged in a circuit, wherein the sensing element comprises a magnetic core having a leading arm, a trailing arm with a gap formed therebetween, and at least one coil wound around the magnetic core and operative to generate, upon connection to a power source, a magnetic field across the gap and to induce an imbalance voltage therein in response to an interaction between the magnetic field and a surface region of a sample, wherein the imbalance voltage is measured to determine a magnetic susceptibility of the surface region, the method comprising measuring an in-plane anisotropy of the sample by:
- (i) passing an alternating electrical current through the coil of the local magnetic susceptibility unit;
- (ii) positioning a region of the sample proximate to the sensing element within a distance from the sensing element effective to induce a voltage perturbation in the coil;
- (iii) measuring the voltage perturbation;
- (iv) rotating the sensing element with respect to the sample;
- (v) measuring a voltage perturbation in the coil;
- and
- (vi) storing the voltage perturbation signal as a function of a rotational position of the sensing element.
A method of measuring the in-plane AC magnetic susceptibility of a surface region of a sample using a local magnetic susceptibility unit comprising a sensing element, one or more balancing elements arranged in a circuit, wherein the sensing element comprises a magnetic core having a leading arm, a trailing arm with a gap formed therebetween, and at least one coil wound around the magnetic core and operative to generate, upon connection to a power source, a magnetic field across the gap and to induce an imbalance voltage therein in response to an interaction between the magnetic field and a surface region of a sample, wherein the imbalance voltage is measured to determine a magnetic susceptibility of the surface region, the method comprising forming a map of the AC magnetic susceptibility by:
- (i) passing an alternating electrical current through the coil of the local magnetic susceptibility unit;
- (ii) positioning a region of the sample proximate to the sensing element within a distance from the sensing element effective to induce a voltage perturbation in the coil;
- (iii) measuring the voltage perturbation:
- (iv) storing the voltage perturbation signal as a function of an x and y position of the sensing element;
- (v) changing the x position and/or the y position of the sensing element;
- and
- (vi) repeating steps (i)-(v).
Dependencies are inferred from the claim text.