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Physical Measurements Service
ACMS option
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ACMS option (Extraction magnetometer)
The ACMS is a versatile DC magnetometer and AC susceptometer. It has an AC-drive coil set that provides an alternating excitation field and a detection coil set that inductively responds to the combined sample moment and excitation field. In addition to the alternating field supplied by the ACMS drive coil, the PPMS platform can apply a constant field during both AC and DC measurements (0 to ± 9 T (PPMS 9T) or to ± 14 T (PPMS 14 T)).
  • Temperature Range: 1.9 K – 350 K.
  • Magnetic Field Range: 0 to ± 9 T, ± 14 T
  • Samples:
    • Liquid.
    • Powder.
    • Films.
    • Pellets.
  • Sample Holde:
    • Straw: powder samples in gelatin capsules or solid samples glued to the Straw
    • ACMS option sample holder: rod screwing into a teflon bucket (in which powder can be poured).
  • DC and AC can be measured along the same sequence.
  • DC mode:
    • Extraction measurement technique
    • During DC measurements, a constant field is applied to the measurement region and the sample is moved quickly through both sets of coils, inducing a signal in them according to Faraday’s Law, producing a characteristic waveform, which is analyzed by software and the magnetic moment is reported.
    • Magnetic moment: 2.5 x 10-5 emu — 5 emu.
  • AC mode:
    • Amplitude: 2 mOe — 17 Oe.
    • Frequency: 10 Hz — 10 KHz. *
    • Sensitivity is frequency dependent: about 10-8 emu at 10 kHz.
    • Allows automatic frequency Scans measurements.


* In AC measurements, at temperatures below 25 K, large amplitude fields may warm the PPMS sample chamber and ACMS insert by induced eddy currents. Maximum applied field to prevent warming depends on temperature, frequency and measurement time.