Piezomagnetism in Cr Dopped Fe65Co35 Alloy

Fe-Co alloys have the highest magnetizations among all existing magnetic materials, 2.45 T for the alloy with 35% Co (% by mass). Regarding magnetostriction, the highest magnetostrictions occurs in Co rich Fe-Co alloys. The piezomagnetic behavior of Fe-Co alloys rich in Fe, that is, the variation of the material's magnetic induction as a function of applied force, was not found in the literature. In the present work, the Fe65Co35 alloy (% by mass) was dopped with 0.5% Cr (% by mass) to inhibit the formation of the bcc cubic ordered phase with B2 structure. The purpose is to retain only the disordered bcc phase with A2 structure, as the ordered phase turn out the material brittle. The saturation magnetostriction was determined 3/2λs = 61 × 10-6 for the dopped alloy and 3/2λs = 26 × 10-6 for the undoped. The enhancement of the magnetostriction imply in an improvement on the magneto mechanical coupling. The magnetic induction as a function of the applied magnetic field was determined for the doped alloy for tensile and compressive stresses (σ) in the range of -100 MPa ≤ σ ≤ 100 MPa and magnetic fields (H) of 0 < H ≤ 5.5 kA/m. From B vs σ curves a sensitivity as high as 6 kA m-1/MPa was achieved for an applied field of only 3 kA/m.