[EN] High mechanical deformation has been induced in a Ni-Mn-In metamagnetic shape memory alloy by means of ball milling. The evolution of both the martensitic transformation and the magnetic properties associated to the microstructural variations has been characterized. The as-milled nanometric particles display an amorphous structure with a frustrated magnetic state compatible with a canonical spin-glass. On heating, an abrupt crystallization process occurs around 500 K leading to a cubic B2 structure, which, in turn, does not show martensitic transformation. Modified Arrott plots point to competing long- and short-range magnetic couplings in the B2 structure. On further heating, a relaxation process takes place above 700 K concurrently with a B2-L21 atomic ordering, giving rise to an anomalous two-step thermal expansion. The combined effect of both processes makes possible the subsequent occurrence of a martensitic transformation, which takes place at the same temperature than in the bulk. The large relative-cooling-power linked to the magnetocaloric effect at the martensitic transformation in the annealed powder makes it interesting for practical applications of magnetic refrigeration at nanoscale.This work has been carried out with the financial support of the Spanish “Ministerio de Economía y Competitividad” (Projects number MAT2012-37923-C02 and MAT2015-65165-C2-R). We also acknowledge ILL and SpINS for beam time allocation (experiment CRG-2158). RCF acknowledges a Postdoctoral fellowship from the Univeridad Pública de Navarra (grant number: 1081/2015). JARV acknowledges CSIC for a JAEdoc contract. J. Pons is acknowledged for TEM observations
