The following options are also included in the MPMS XL-5.

1. With the use of external device control option, MPMS XL-5 serves as an experimental platform for the measurement of magnetoresistance and Hall effect.
2. Through ac susceptibility measurement option MPMS XL-5 can be used for ac magnetic susceptibility measurement; the ac frequency range is between 0.01 Hz and 1 kHz. and the strength of ac field is between 0.2 mOe and 2 Oe. The output voltage is proportional to the magnetic flux in the pickup coil instead of its time derivative, which leads to a minimal variation in sensitivity over the entire frequency range: sensitivity is 5 x 10^-8 emu. This is in contrast to conventional ac systems where signal sensitivity depends on measurement frequency.
3. The vertical sample rotator permits users of the transverse superconducting coil set to rotate samples ± 360 degrees about the longitudinal axis of the solenoid under computer control. The horizontal sample rotator is used for rotating a sample with respect to the magnetic field. This option, which requires the vertical sample rotator, will rotate a thin film for measuring the magnetic moment versus angular position.
4. Magnetic fields in the MPMS XL-5 are produced by precisely controlling current in the superconducting solenoid. Typically, a residual or remanent field of 0.3 to 1 Oe remains in the superconducting solenoid after operation at high field-even the current is oscillated to zero. The ultra-low field capability option actively cancels residual magnetic flux so samples can be cooled in a very low field, typically less than 3 mOe. This capability is extremely important for measurements of spin glass materials and high T_c superconductors. This option requires use of the environmental magnetic shield option which both reduces excessive environmental magnetic noise and screens out the Earth's ambient field.

Here we show two techniques for measurements of magnetization and ac magnetic susceptibility which becomes possible only through the use of MPMS XL-5.

(a) ac SQUID magnetic susceptibility. The ac susceptibility is especially important for systems with spin frustration effects such as spin glass and cluster glass phases, since ac driving field h can be made very small (= 2 x 10^-4 - 2 Oe) and f can be varied over a rather large frequency range (f = 0.01 Hz - 1 kHz), thereby permitting a full determination of the real c'(w), the dispersion, and imaginary c''(w) part, the absorption (w = 2pf). Through ac susceptibility measurement option MPMS XL-5 can be used for ac magnetic susceptibility measurement: the ac frequency range is between 0.01 Hz and 1 kHz and the strength of ac field is between 0.2 mOe and 2 Oe. The output voltage is proportional to the magnetic flux in the pickup coil instead of its time derivative, which leads to a minimal variation in sensitivity over the entire frequency range: sensitivity is 5 x 10^-8 emu. This is in contrast to conventional ac systems where signal sensitivity depends on measurement frequency.

(b) FC and ZFC magnetization measurements. There are two distinct ways to measure the magnetization with a small dc field by SQUID magnetometer. The field cooling (FC) method is to apply the field far above a characteristic temperature T_f and cool the sample in a field to T << T_f, all the while recording the magnetization. The zero field cooling (ZFC) is to cool the sample in zero field to T << T_f, and at this low temperature apply the field. Then one can heat the sample while measuring M to T >> T_f with the field constant. For spin glass and cluster glass phases, a highly irreversible, metastable frozen state may occur below T_f without a usual long-range spatial spin order. The dc field less than 1 Oe, if applied below T_c, creates a metastable, irreversible state, and T_f is nicely defined by the onset of these irreversibilities. The difference between ZFC and FC magnetization indicates that the free energy has a complicated many valley structure below T_f. The remnant magnetic field of less than 3 mOe is the key to the precise measurement of FC and ZFC magnetizations.

Information proivded by: http://www.binghamton.edu