Development of Techniques for the Dielectric Constant Measurement in Matter in Ultrahigh Magnetic Fields Exceeding 100 T

Materials Science Condensed Matter Physics Physics
ultrahigh magnetic fields dielectric constant radio frequency modulation single-turn coil ferroelectric material

Academic Background

Studying the physical properties of materials under extreme conditions is one of the important directions in condensed matter physics. Ultrahigh magnetic fields (exceeding 100 Tesla) can significantly alter the behavior of electrons in materials, for example, by influencing the electronic and crystal structures through the Zeeman effect and cyclotron motion. However, the generation and measurement of ultrahigh magnetic fields face significant technical challenges, especially in the measurement of dielectric constants. The dielectric constant (ε) is a crucial parameter that reflects a material’s ability to respond to an external electric field, revealing insights into its internal charge distribution and polarization properties. In ferroelectric materials, changes in the dielectric constant are often related to the instability of the crystal structure, particularly near the ferroelectric phase transition.

However, techniques for measuring dielectric constants under ultrahigh magnetic fields are still underdeveloped. Due to the extremely short duration of ultrahigh magnetic fields (typically a few microseconds), traditional measurement methods are not applicable. Therefore, developing a technique capable of accurately measuring dielectric constants under ultrahigh magnetic fields has become a core challenge in this field. This study aims to fill this technological gap by successfully achieving dielectric constant measurements in ultrahigh magnetic fields exceeding 100 Tesla using radio frequency (RF) modulation technology.

Source of the Paper

This paper was co-authored by Polin Chiu, Yuto Ishii, and Yasuhiro H. Matsuda from the Institute for Solid State Physics, University of Tokyo. The paper was published on April 16, 2025, in the Journal of Applied Physics, titled “Development of Techniques for the Dielectric Constant Measurement in Matter in Ultrahigh Magnetic Fields Exceeding 100 T,” with the DOI 10.1063⁄5.0246641.

Research Process

1. Technique Development

This study first developed a dielectric constant measurement technique based on RF modulation. Ultrahigh magnetic fields were generated using the single-turn coil (STC) technique, which discharges a high-voltage capacitor bank to produce instantaneous magnetic fields. Due to the extremely short duration of the magnetic field (approximately 7 microseconds), traditional low-frequency measurement methods were not applicable. Therefore, the research team designed a high-frequency (30-50 MHz) RF modulation system to perform rapid measurements during the magnetic field pulse.

The measurement system included an RF signal generator (SG382), a dielectric constant measurement probe, and an oscilloscope (HDO6054). To reduce electromagnetic noise and mechanical interference, the research team employed filters, impedance matching, and mechanical isolation designs. Additionally, to avoid thermal effects, the RF signal input was pulse-controlled, with a pulse width set to 20 microseconds, covering the duration of the magnetic field pulse.

2. Sample and Experimental Setup

The research team selected the typical ferroelectric material barium titanate (BaTiO3, BTO) as the experimental sample. BTO undergoes a phase transition from the paraelectric phase to the ferroelectric phase near 393 K, with a significant increase in dielectric constant near the transition temperature. The experimental sample was a 1.5 × 1.5 × 1 mm³ single crystal of BTO, with 50 nm thick gold electrodes sputtered on both ends, connected to the measurement probe via gold wires.

3. Ultrahigh Magnetic Field Experiments

The experiments were conducted at the ultrahigh magnetic field laboratory of the University of Tokyo, with magnetic field strengths reaching up to 120 Tesla. The research team measured the changes in the dielectric constant of BTO at different temperatures and magnetic fields, focusing on the relationship between the magnetic field direction and the ferroelectric polarization direction. The experimental results showed that when the magnetic field direction was parallel to the polarization direction, the dielectric constant significantly decreased at magnetic fields exceeding 100 Tesla; whereas, when the magnetic field direction was perpendicular to the polarization direction, the dielectric constant remained almost unchanged.

Main Results

  1. Validation of the Dielectric Constant Measurement Technique: The research team first validated the effectiveness of the measurement technique at zero magnetic field. By measuring the RF spectra of different capacitors, the team found that the resonant frequency exhibited significant dependence on the capacitance value, demonstrating the high sensitivity of the technique.

  2. Temperature Dependence Measurement: At zero magnetic field, the research team measured the changes in the dielectric constant of BTO near the phase transition temperature, with results consistent with existing literature, verifying the accuracy of the measurement system.

  3. Dielectric Constant Changes under Ultrahigh Magnetic Fields: In the magnetic field experiments, the research team observed that when the magnetic field direction was parallel to the polarization direction, the dielectric constant significantly decreased at magnetic fields exceeding 100 Tesla. This phenomenon suggests that ultrahigh magnetic fields may stabilize the ferroelectric phase by influencing the wave function mixing of titanium (Ti) and oxygen (O) ions, leading to a slight increase in the phase transition temperature (Tc).

Conclusions and Significance

This study successfully developed a technique for measuring dielectric constants under ultrahigh magnetic fields and, for the first time, observed significant changes in the dielectric constant of BTO in magnetic fields exceeding 100 Tesla. This discovery not only provides new experimental evidence for understanding the physical properties of ferroelectric materials under ultrahigh magnetic fields but also opens new research directions for exploring the non-perturbative effects of magnetic fields on covalency.

Research Highlights

  1. Technological Innovation: The high-frequency RF modulation technique developed in this study fills the gap in dielectric constant measurement technology under ultrahigh magnetic fields, providing new experimental tools for material research under extreme conditions.
  2. Key Findings: The first observation of significant changes in the dielectric constant of BTO under ultrahigh magnetic fields reveals the influence of magnetic fields on ferroelectric phase transitions.
  3. Scientific Value: The research results provide new experimental evidence for understanding the electronic and crystal structures of materials under ultrahigh magnetic fields, advancing the development of condensed matter physics under extreme conditions.

Additional Valuable Information

The experimental data and analysis methods of this study have been made publicly available in the supplementary materials. Interested readers can obtain detailed data by contacting the authors. Additionally, the research team plans to further explore the behavior of other ferroelectric materials under ultrahigh magnetic fields to validate the universality of this technique and expand its application scope.

Through this study, we have not only deepened our understanding of material behavior under ultrahigh magnetic fields but also provided important technical support and theoretical guidance for future experimental research under extreme conditions.