Inspection Probes of a Scanning Ferromagnetic Resonance Spectrometer

Abstract

An inspection probe is the key component of a scanning ferromagnetic resonance spectrometer, which is used to measure spectra of electromagnetic radiation absorption in local areas of thin magnetic films. The degree of locality is determined by the area of the measuring aperture in a probe (0.1–2.2 mm²). The spectrometer sensitivity has been significantly increased by miniaturizing the oscillating circuit with a high intrinsic quality factor of the autodyne oscillator and by replacing the round measuring aperture of the probe head with a square one. The square shape of the measuring aperture increases the homogeneity of the high-frequency magnetic field distribution in it. A set of replaceable probes with a required pitch has been designed to cover the frequency range of 0.1–4.0 GHz. The signal-to-noise ratio of a probe with an aperture area 1.0 mm², measured on a permalloy film with a thickness of 2 nm is 8 dB or more. It is shown that the effective saturation magnetization monotonically reaches the saturation M_S = 843 G with frequency rise and abnormally increases by a factor of ~1.6, to M_S = 1359 G at low frequencies. The applicability of the developed probes to study the nature of formation and the peculiarities of the magnetic-inhomogeneity distribution over a sample area is demonstrated by using 25-nm-thick permalloy films (dimensions, 10 × 10 mm²) deposited in a dc magnetic field on monocrystalline langasite substrates.