Harmonic detection of multipole moments and absolute calibration in a simple, low-cost vibrating sample magnetometer

The design and fabrication of a low-cost, highly sensitive, fully automated vibrating sample magnetometer for dc magnetization measurements is describ ed. Harmonic detection of magnetic multipole moments is demonstrated experi mentally in an inhomogeneously magnetized nickel sample at room temperature and in a gadolinium sample across the magnetic phase transition. A method is presented to nullify the earth's effective field even without any shield ing. More significant, the setup uses only one lock-in amplifier for signal detection, vibration excitation, and temperature measurement and control. First principles calculations give an absolute determination of the instrum ental conversion factor that agrees with the experimental calibration facto r. The setup is stable from 77 to 300 K, the overall sensitivity is less th an or equal to 5 x 10(-6) emu, and the reproducibility is less than or equa l to 1%. (C) 1999 American Institute of Physics. [S0034-6748(99)00301-9].