Phase transition, microstructure, magnetic properties and microwave absorbing properties of La_xNd_35-xFe₆₅ alloys

For exploring the effect of La substitution on the absorption properties of La_xNd_35-xFe₆₅ alloy, the La_xNd_35-xFe₆₅ (x=4, 9, 19, 29) powder was systematically studied by using mechanical alloy method. The crystal structure and microstructure were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The magnetic properties and microwave absorption properties were determined by vibrating sample magnetometer (VSM) and vector network analyzer (VNA), respectively. When the La content changes from 4 to 9, the main phase of La_xNd_35-xFe₆₅ alloys transforms from Nd₅Fe₁₇ to Nd₂Fe₁₇ phase. With the further increase of La content, the main phase of La_xNd_35-xFe₆₅ alloys are still Nd₂Fe₁₇ phase, but the second phase changes from α-Nd phase to α-La phase. At the same time, the saturation magnetization of the La_xNd_35-xFe₆₅ alloys decreases first and then increases slowly, and the reflection peak moves to the higher frequency region first and then the lower frequency region. The La₄Nd₃₁Fe₆₅ powder exhibits excellent microwave absorption performance, the minimum value of its reflection loss can reach −31.54 dB when at the peak frequency of 8.2 GHz, and the effective bandwidth(reflection loss less than −10 dB) can reach 1.44 GHz with the matching thickness d = 1.6 mm.