ABSTRACT: We describe a multifrequency quasi-optical electron spin resonance (ESR) spectrometer operating in the 75–225GHz range and
optimized at 222.4GHz for general use in condensed matter physics and chemistry. The quasi-optical bridge detects the change
of millimeter wave polarization at the ESR condition. A controllable reference arm maintains a millimeter wave bias at the
detector. The sensitivity of 2×1010spin/(GHz0.5), measured on a dilute Mn:MgO sample in a non-resonant probe head at 222.4GHz and 300K, is comparable to that of commercial
high-sensitive X-band spectrometers. The spectrometer is robust, easy to use and may be operated by undergraduate students.
Its performance is demonstrated by examples from various fields of condensed matter physics.
Applied Magnetic Resonance 05/2012; 40(1):47-63. · 0.75 Impact Factor