  Direct measurements of the magnetocaloric effect in samples of rapidly
quenched ribbons of Mn50Ni40In10 and Ni50Mn37Sn13 Heusler alloys, with
potential applications in magnetic refrigeration technology, are carried out.
The measurements were made by a precise method based on the measurement of the
oscillation amplitude of the temperature in the sample while is subjected to a
modulated magnetic field. In the studied compositions both direct and inverse
magnetocaloric effects associated with magnetic (paramagnet - ferromagnet -
antiferromagnet) and structural (austenite - martensite) phase transitions are
found. Additional inverse magnetocaloric effects of small value are observed
around the ferromagnetic transitions.
