Ni 2 MnGa thin films have been grown pseudomorphically on a 6-monolayer thick Sc 0.3 Er 0.7 As interlayer on GaAs001 by molecular-beam epitaxy. They have a tetragonal structure ab 5.65 Å and c6.18 Å which is different from any of the known bulk phases. Magnetic measurements reveal Ni 2 MnGa to have an in-plane easy axis and a Curie temperature around 350 K. The magnetic properties of these films are given and compared to the corresponding measurements in bulk material. In contrast to bulk material, single crystal films have been predicted to exhibit exact austenite–martensite interfaces without fine twinning of the martensite. Films have been patterned along the predicted interfaces using the conventional photolithography and reactive ion etching. The patterns are then released from the substrate by backside photolithography and selective wet chemical etching, to yield freestanding films. The martensitic transformation of the freestanding films has been observed slightly above the room temperature. Magnetic domain observations by MFM on the martensitic films are presented. © 2002 American Institute of Physics.