| Popis: |
The measurements of magnetization M ( T ) in bulk SDW alloys Cr 1 - x Co x and ( Cr + 2.7 % Fe ) 1 - x Co x in ZFC and FC states in magnetic field 100 Oe with a SQUID magnetometer have revealed two types of magnetic irreversibility (thermal hysteresis between magnetization measured in FC and ZFC states, M FC ( T ) , M ZFC ( T ) ). The first one is observed in alloys with both incommensurate (I) and commensurate (C) SDW structures below the temperature T i much lower than the Neel temperature, T N . It has been explained in terms of a short range SDW order (“local SDW'') on the defect. The second one is observed below T i ∼ T N only for Cr alloys with the I-SDW structure. It has been attributed to the mechanism of the SDW phase slip on the defect inside the “SDW soliton wall''. Depending on the field cooled procedure the alloy Cr+1.19% Co with the I-SDW structure shows the first or the second type of magnetic irreversibility, however, if the C-SDW phase is induced by Fe-doping only the first type of magnetic irreversibility can be observed. The temperature dependence of the remanent magnetization, M Rem ( T ) , observed in all studied alloys can be well simulated using the proposed models. |
Full Text from ScienceDirect