Susceptometer and process for determining magnetic susceptibility
Inventors
Assignees
United States Department of Commerce
Publication Number
US-9714991-B2
Publication Date
2017-07-25
Expiration Date
2036-03-03
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Abstract
A susceptometer includes: a substrate; a plurality of electrodes including: a first pair of electrodes disposed on the substrate; a second pair of electrodes disposed on the substrate, the second pair of electrodes arranged collinear with the first pair of electrodes to form a set of aligned electrodes; and a third pair of electrodes disposed on the substrate, the third pair of electrodes arranged noncollinearly with set of aligned electrodes; and a solenoid circumscribingly disposed around the electrodes to: receive the sample such that the solenoid is circumscribingly disposed around the sample; receive an alternating current and produce an primary magnetic field based on the alternating current; and subject the sample to the primary magnetic field.
Core Innovation
The invention is a susceptometer including a substrate with a plurality of electrodes configured to subject a sample to a direct current electrical current and measure at least one of the Hall voltage or current-in-plane resistance of the sample. These electrodes include a first pair and a second pair arranged collinearly to form a set of aligned electrodes, and a third pair arranged noncollinearly with the set of aligned electrodes. The susceptometer also includes a solenoid circumscribingly disposed around the electrodes to receive the sample, receive an alternating current, produce a primary magnetic field based on the alternating current, and subject the sample to this primary magnetic field.
The susceptometer includes features such as a chamber housing the substrate, electrodes, and solenoid. The electrodes are electrically reconfigurable in-situ to obtain reconfigurably the Hall voltage and current-in-plane resistance while subjecting the sample to a direct current. The construction allows the solenoid to produce a time-varying primary magnetic field perpendicular to the surface of the sample in contact with the electrodes. The susceptometer is capable of performing magnetic susceptometry on thin semiconducting or ferromagnetic films.
The problem addressed by this invention involves the need to measure magnetic susceptibility and magnetoelectronic properties of thin film samples, such as semiconductors or ferromagnetic materials, with improved accuracy and flexibility. Existing devices may not provide the ability to electrically reconfigure electrodes in-situ or to apply both AC magnetic excitation and DC electrical current in a compact, integrated configuration. The susceptometer addresses these issues by combining a configured plurality of electrodes with a solenoid that produces a primary magnetic field, enabling simultaneous and reconfigurable measurement of Hall voltage and current-in-plane resistance of the sample under controlled magnetic excitation.
Claims Coverage
The patent claims three independent claims that cover the susceptometer device, a susceptometer for magnetic susceptometry, and a process for performing magnetic susceptometry. The main inventive features include the arrangement and function of the electrodes, the solenoid circumscribing the sample and electrodes, and the electrical reconfiguration capability for Hall voltage and resistance measurements.
Electrodes arrangement and measurement capabilities
A plurality of electrodes disposed on a substrate including a first pair, a second pair collinear with the first to form aligned electrodes, and a third pair arranged noncollinearly; electrically conductive to engage and be in electrical contact with a sample to subject it to a direct current and measure at least one of Hall voltage or current-in-plane resistance.
Solenoid configuration and magnetic field application
A solenoid circumscribingly disposed around the electrodes and sample to receive an alternating current, produce a primary magnetic field based on the alternating current, and subject the sample to this primary magnetic field.
Electrical reconfiguration in-situ of electrodes
Electrodes being electrically reconfigurable in-situ and in contact with the sample to obtain reconfigurably the Hall voltage and the current-in-plane resistance of the sample while subjecting it to direct current electrical current.
Additional electrode pairs and their arrangement for Hall voltage measurement
Inclusion of a fourth pair of electrodes arranged noncollinearly with the aligned electrodes and forming a square pattern with the third pair to obtain a Hall voltage from the sample.
System features including chambers, magnet and heater
The susceptometer's housing in a chamber; optionally including an external magnet for providing a secondary magnetic field; optionally including a heater proximate to the sample; and optionally including a switching member to switch electrode configurations between resistance and Hall voltage modes.
Process for performing magnetic susceptometry
Providing the sample to a susceptometer with the specified electrode arrangement and solenoid; receiving the sample in the solenoid; providing an alternating current to produce a primary magnetic field; subjecting the sample to the primary magnetic field and direct current electrical current; and measuring Hall voltage or current-in-plane resistance.
The claims comprehensively cover the susceptometer structure with specifically arranged electrode pairs enabling reconfigurable electrical measurements in combination with a solenoid generating a primary magnetic field around the sample. The patent also claims the method of using such a susceptometer to perform magnetic susceptometry measurements.
Stated Advantages
Ability to perform magnetic susceptibility measurements on thin semiconducting or ferromagnetic films with simultaneous application of AC magnetic field and DC electrical current.
Electrical reconfiguration of electrodes in-situ to obtain Hall voltage and current-in-plane resistance measurements without breaking contact with the sample.
Capability to control temperature of the sample for susceptibility measurements.
Improved electromagnetic noise reduction by choosing material composition for chamber components.
Provision of complex measurements including harmonic susceptibilities, AC and DC Hall effects, and magnetoresistance measurements.
Robust and time-saving mechanical mounting configurations for the sample and electrode positioning.
Automation and unattended operation with integrated electronic control and data analysis.
Calibration of AC measurements using coil geometry, enabling accurate determination of magnetic properties.
Documented Applications
Performing magnetic susceptometry on thin film samples, including semiconductor thin films, ferromagnetic thin films, or combinations thereof.
Measuring the Hall voltage or current-in-plane resistance of a sample under an alternating magnetic field for magnetic susceptibility analysis.
Analyzing magnetoelectronic properties such as anomalous magnetoresistance, giant magnetoresistance, planar or extraordinary Hall effects in thin film samples.
Use in systems to study magnetic sensor signal-to-noise ratios across frequency ranges using controlled AC excitation fields.
Studying magnetic susceptibility changes during remagnetization and obtaining first order reversal curves.
Temperature controlled magnetic and electrical property measurements of samples at operating and elevated temperatures.
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