Magnetization and Superconducting Quantum Interference Device detected Electron Paramagnetic Resonance (SQUID-EPR) of the FIN Trityl Radical

Published

January 24, 2009

Author(s)

Brant Cage, James H. McNeely, Howard J. Halpern, Stephen E. Russek

Abstract

The Finland trityl paramagnet is characterized by magnetic susceptibility and a new form of quantitative electron paramagnetic resonance (EPR) that utilizes a superconducting quantum interference device (SQUID) as a detection method. This radical is of interest due to its use as a dynamic nuclear polarization agent as well as a potential magnetic refrigerant and quantum computing bit. The SQUID-EPR data show that the EPR linewidth of a concentrated trityl powder decreases dramatically from 4.4 to 1.4 mT as the temperature is increased from 1.8 to 10 K. The quantitative nature of SQUID-EPR is used to thermodynamically quantify the EPR energy transfer times and saturated fractions. At 95 GHz and 1.8 K, only 40% of the spins are in resonance at the onset of saturation. Conventional dc magnetic susceptibility over 1.8–150 K indicates an S=1/2 Curie-Weiss relationship with little long range interaction. Magnetization versus applied field at 1.8 and 4 K fits a Brillouin function with >80% electronic polarization at a normalized field of gυ_Bυ₀H/kTapproximately equal}3. These results provide information required for theoretical modeling and engineering of the trityl radical for a wide range of applications.

Citation

Journal of Applied Physics

Volume

105

Issue

043905

Pub Type

Journals

Keywords

DNP, SQUID-EPR, Trityl

Citation

Cage, B. , McNeely, J. , Halpern, H. and Russek, S. (2009), Magnetization and Superconducting Quantum Interference Device detected Electron Paramagnetic Resonance (SQUID-EPR) of the FIN Trityl Radical, Journal of Applied Physics (Accessed October 7, 2025)