Measurement of magnetic susceptibility in pulsed magnetic fields using a proximity detector oscillator

Abstract

We present a novel susceptometer with a particularly small spatial footprint and no moving parts. The susceptometer is suitable for use in systems with limited space where magnetic measurements may not have been previously possible, such as in pressure cells and rotators, as well as in extremely high pulsed fields. The susceptometer is based on the proximity detector oscillator, which has a broad dynamic resonant frequency range and has so far been used predominantly for transport measurements. We show that for insulating samples, the resonance frequency behavior as a function of field consists of a magnetoresistive and an inductive component, originating, respectively, from the sensor coil and the sample. The response of the coil is modeled, and upon subtraction of the magnetoresistive component the dynamic magnetic susceptibility and magnetization can be extracted. We successfully measure the magnetization of the organic molecular magnets Cu(H(2)O)(5)(VOF(4))(H(2)O) and [Cu(HF(2))(pyz)(2)]BF(4) in pulsed magnetic fields and by comparing the results to that from a traditional extraction susceptometer confirm that the new system can be used to measure and observe magnetic susceptibilities and phase transitions.

Spin susceptibility of charge-ordered YBa 2 Cu 3 O y across the upper critical field

“…This then shifts the resonance frequency f res of the NMR tank circuit. In its basic principle, the method is analogous to contactless measurements using diode-oscillators [63]. …”

“…Vortex melting can be probed with the NMR setup: the rapid change in resistivity across the melting line modifies the skin depth of the sample, which in turn produces a change of the inductance of the NMR coil surrounding the sample [63]. This then shifts the resonance frequency f res of the NMR tank circuit.…”

Fermi-surface topologies and low-temperature phases of the filled skutterudite compoundsCeOs4Sb12andNdOs4Sb12

“…A change in the sample skin depth 18 or differential susceptibility 17 causes a change in the inductance of the coil, which in turn alters the resonant frequency of the circuit. Shubnikov-de Haas oscillations are observed in the resistivity and hence the skin depth and frequency 17,18 . For the purposes of digitizing the data prior to Fourier transformation to obtain the frequency as a function of field, the signal from the PDO circuit is mixed down to about 2 MHz using a double heterodyne system 17,18 .…”

“…Shubnikov-de Haas oscillations are observed in the resistivity and hence the skin depth and frequency 17,18 . For the purposes of digitizing the data prior to Fourier transformation to obtain the frequency as a function of field, the signal from the PDO circuit is mixed down to about 2 MHz using a double heterodyne system 17,18 . Data are recorded at 20 Msamples/s, well above the Nyquist limit.…”

Robustness of superconductivity to structural disorder inSr0.3(NH2)y(NH3)1Foronda1, Ghannadzadeh2, Sedlmaier3 et al. 2015Phys. Rev. BSelf Cite9040View full textAdd to dashboardCite

“…Powder samples were measured at the Nicholas Kurti Magnetic Field Laboratory, Oxford using a proximity detector oscillator (PDO) dynamic susceptometer [20,21]. The sample is mounted in an ampoule under an argon atmosphere and placed inside a small sensor coil that is inductively coupled to the PDO circuit.…”