SquidLab—A user-friendly program for background subtraction and fitting of magnetization data

Abstract

We present an open-source program free to download for academic use with full user-friendly graphical interface for performing flexible and robust background subtraction and dipole fitting on magnetization data. For magnetic samples with small moment sizes or sample environments with large or asymmetric magnetic backgrounds, it can become necessary to separate background and sample contributions to each measured raw voltage measurement before fitting the dipole signal to extract magnetic moments. Originally designed for use with pressure cells on a Quantum Design MPMS3 SQUID magnetometer, SquidLab is a modular object-oriented platform implemented in Matlab with a range of importers for different widely-available magnetometer systems (including MPMS, MPMS-XL, MPMS-IQuantum, MPMS3 and S700X models), and has been tested with a broad variety of background and signal types. The software allows background subtraction of baseline signals, signal preprocessing, and performing fits to dipole data using Levenberg-Marquadt non-linear least squares, or a singular value decomposition linear algebra algorithm which excels at picking out noisy or weak dipole signals. A plugin system allows users to easily extend the built-in functionality with their own importers, processes or fitting algorithms. SquidLab can be downloaded, under Academic License, from the University of Warwick depository (wrap.warwick.ac.uk/129665).

Kagome van-der-Waals Pd3P2S8 with flat band

“…S3 online) 41,42 . Afterward, we undertook the susceptibility measurement to find that it exhibits a sizeable diamagnetic response below the room temperature, as shown in Figure 2a and 2b 43 (see also Supplementary Fig. S4).…”

“…For some measurement sets with the thin glass support, the background signals were subtracted off from the raw data to obtain the pure sample signals and to ensure that the significant signals were from the sample alone. The subtraction was done using the SquidLab software suite, which was developed to improve the fidelity of the signals during this project 43 . The magnetization was measured in two ways: the field sweeping at a specific temperature and the temperature sweeping with a particular applied field.…”

Hydrostatic and Uniaxial Pressure Tuning of Iron‐Based Superconductors: Insights into Superconductivity, Magnetism, Nematicity, and Collapsed Tetragonal Transitions

“…A big challenge here is to subtract the sizable background contribution of the pressure cell from the measured signal. [106] Alternatively, measurements of the magnetic susceptibility by using an ac technique can be performed inside a pressure cell. Certainly, this technique is not as sensitive to small moments as the commercial superconducting quantum interference device (SQUID)-based MPMS, but it offers the possibility to measure frequency-dependent magnetic properties, which can be of relevance for, for example, spin glasses [107] and has the great potential for significant miniaturization, which is essential for application at even higher pressures.…”

Unexpectedly Strong Diamagnetism of Self-Assembled Aromatic Peptides

“…The magnetic field was swept between -30,000 Oe and 30,000 Oe with one measurement point per 2500 Oe. All DC magnetic susceptibilities were corrected for diamagnetic contribution from the sample holder, and the solvent (water or salt aqueous solution) by directly subtracting their scaled voltage signals by weight and then fitting with a SquidLab program [17] . As the result, we can get the magnetization (M) versus magnetic field (H) curves, and compute the mass susceptibility (χ), χ = M/H=a/mH, where a is the moment measured by the SQUID magnetometer and m is the mass of the assembled peptide measured by a Nanophotometer TM P330 (Implen GmbH).…”