Very large magnetoimpedance effect in FeCoNi ferromagnetic tubes with highorder magnetic anisotropy

The extraordinarily high (up to 800% magnetoimpedance ratio) and sensitive magnetoimpedance effect has been found and studied in FeCoNi magnetic tubes electroplated onto CuBe nonmagnetic wire at frequency of about 1 MHz order . Special annealing was done in order to induce magnetic anisotropy. The hi gh harmonic response has been studied, and the harmonics show larger variat ions with the external magnetic field than the fundamental. This huge sensi tivity of the harmonics (up to an order of the tens of thousands %/Oe) is p romising in regard to the increase of the sensitivity of giant magnetoimped ance sensors. To explain the experiment results, we calculated the high fre quency transverse susceptibility taking into account the magnetic anisotrop y of first and second orders. The susceptibility is extremely high at the p oints of orientational phase transitions in the magnetic layer which gives rise to strong nonlinear effects. (C) 2001 American Institute of Physics.