A New Zero‐Field Paramagnetic Resonance Spectrometer
The construction of a new zero‐field paramagnetic resonance (ZFPMR) spectrometer is discussed. Spectrometer organization and construction details are presented for both resonant cavities and broadband traveling‐wave helices as sample holders. A new circuit diagram for a square wave magnetic field modulator with fast rise time is given. The performance of each kind of spectrometer is discussed with particular emphasis on investigation of paramagnetic rare earth ions with zero‐field splittings in diamagnetic host lattices.
Broadband Millimeter Wave Paramagnetic Resonance Spectrometer
A flexible magnetic resonance spectrometer is described. Its transmission type microwave structure can be used between 50 and 150 kMc. A modified Varian magnet gives a field of 28 000 gauss, homogeneous to 3 gauss over a typical sample area. A Dewar vessel fits into the 34-in. magnet gap and permits cooling of the sample below the λ point of helium. The millimeter waves are generated by backward wave oscillators, and harmonic conversion is used for the frequency measurement and control. A modification of the spectrometer makes possible the direct measurement of line width and frequency of zero-field lines.
Temperature Effects on Zircon Structure Lattice Parameters and Zero‐Field Resonance for Substituted Gd3+
The linear expansion coefficients of the unit cell of several zircon structure crystals were determined from high-temperature X-ray data and compared with the temperature dependence of the rotational parameters in the corresponding spin Hamiltonian for Gd3−, taken from zero-field resonance work. 
 
 
 
Die linearen Ausdehnungskoeffizienten der Elementarzelle einiger Kristalle mit Zirkonstruktur wurden mit Hilfe von Hochtemperatur-Rontgenmethoden gemessen und mit den Temperaturkoeffizienten der rotationssymmetrischen Anteile des Spin-Hamiltonoperators fur Gd3+ verglichen. Diese Parameter wurden aus Nullfeldresonanz-Messungen erhalten.