Fig. 4.

Linear shape memory effect and thermal actuation in cryogenic environments. a The temperature-pressure phase diagram for CaFe₂As₂ ²², neutron scattering data of b (004)_O plane of orthorhombic phase at T = 50 K with increasing pressure, c (004)_cT plane of collapsed tetragonal phase at T = 50 K with increasing pressure, d (004)_cT plane of collapsed tetragonal phase at T = 50 K with decreasing pressure, e (004)_O plane of orthorhombic phase at T = 50 K and p = 50 MPa, f (004)_cT plane of collapsed tetragonal phase at p = 300 MPa with increasing temperature, g (004) planes of tetragonal and collapsed tetragonal phases at p = 470 MPa with increasing and decreasing temperature. Schematic diagrams of h one way linear shape memory effect and i thermal actuation