Experiments exploring the Magnetic Barkhausen Noise (MBN) during the martensitic transformation led to the discovery of a novel phenomenon, here called "Spontaneous magnetic emission" (SME). This new phenomenon was identified while testing the hypothesis that there would be a Barkhausen Noise-like magnetic emission as a consequence of the movement of Bloch walls in the newly formed ferromagnetic martensite, as the nucleation and growth of Weiss magnetic domains followed the growth of martensite plates. The SME hypothesis was demonstrated experimentally in a Fe-Ni-C alloy, austenitic at room temperature, while being cooled to liquid nitrogen temperature. © 2012 Published by Elsevier B.V.