Correlation between magnetoimpedance and permeability in La2/3Ba1/3MnO3

Even though the dc magnetoresistance Δρ/ρ0 is only −4.2% under 8 kOe, La2/3Ba1/3MnO3 manganite sintered at 1280 °C could present a huge ac magnetoresistance ΔR/R0=−43.3% at 10 MHz, a large magnetoreactance ΔX/X0=−37.3% at 200 kHz and a giant magnetoimpedance ΔZ/Z0=−30% at 4 MHz under a low field H=600 Oe at room temperature. There is a correlation between giant magnetoimpedance effect and permeability change. Both resistance R   and circular imaginary permeability μϕ″ decrease with an increase of field at frequencies f≤30 MHz. The reactance X decreases with increasing field at frequencies f≤20 MHz, meanwhile the circular real permeability μϕ′ monotonically drops. At a high frequency of 30 MHz, both X   and μϕ′ experience a small peak with an increase of field. With an increase of ac frequency, under a field of 600 Oe the magnetoresistance ΔR/R0 increases at first, undergoes a maximum at 10 MHz, and then drops, while magnetoreactance ΔX/X0 shows an almost monotonous decrease at frequencies above 1 MHz. Correspondingly, the change of circular imaginary permeability Δμϕ″/μϕ″(0) under 600 Oe undergoes a maximum of −92.6% at 4 MHz and then drops with frequency, while the change of circular real permeability Δμϕ′/μϕ′(0) drops monotonically from −67.9% at 500 kHz to −11.7% at 30 MHz. The magnetoresistance is mainly dominated by the change of transverse imaginary permeability, while the magnetoreactance is mainly controlled by the change of transverse real permeability.

Research highlights
► La2/3Ba1/3MnO3 presents a giant magnetoimpedance of −30% at 4 MHz under 600 Oe at room temperature.
► The change of circular real permeability could reach −67.9% at 500 kHz under 600 Oe.
► The change of circular imaginary permeability could reach −92.6% at 4 MHz under 600 Oe.
► The magnetoresistance is mainly dominated by the change of transverse imaginary permeability.
► The magnetoreactance is mainly controlled by the change of transverse real permeability.