  We demonstrate detection of broadband intense terahertz electromagnetic
pulses by Zeeman-torque sampling (ZTS). Our approach is based on magneto-optic
probing of the Zeeman torque the terahertz magnetic field exerts on the
magnetization of a ferromagnet. Using an 8 nm thick iron film as sensor, we
detect pulses from a silicon-based spintronic terahertz emitter with bandwidth
0.1-11 THz and peak field >0.1 MV/cm. Static calibration provides access to
absolute transient THz field strengths. We show relevant added values of ZTS
compared to electro-optic sampling (EOS): an absolute and echo-free transfer
function with simple frequency dependence, linearity even at high terahertz
field amplitudes, the straightforward calibration of EOS response functions and
the modulation of the polarization-sensitive direction by an external AC
magnetic field. Consequently, ZTS has interesting applications even beyond the
accurate characterization of broadband high-field terahertz pulses for
nonlinear terahertz spectroscopy.
