Temperature dependence of the magnetic properties of mono-dispersed Co _0.5 Zn _0.5 Fe ₂ O ₄ microtubes derived from different templates

In this work, the Co _0.5 Zn _0.5 Fe ₂ O ₄ microtube was prepared via a template-assembled sol–gel method, where three kinds of natural fiber worked as template. Effect of template types on morphology, specific area, and magnetic properties under different temperatures of ferrites microtube was investigated. XRD results confirm the formation of pure spinel Co _0.5 Zn _0.5 Fe ₂ O ₄ ; SEM results proves that the CZF-microtubes is mono-dispersed and exactly copies the morphology of the corresponding template. It possesses excellent magnetic properties (M _s , 62.62 emu g ⁻¹ ) and higher specific area (51.11 m ²  g ⁻¹ ), respectively, the former is mainly due to the net-liked microstructure and distribution of higher magnetic magneton cation in crystal cell, and the latter is attributed to not only the smaller grain size, but also the stack manner of nanoparticles. Below Curie temperature, coercivity of CZF-microtubes decreases with an increased temperatures in accordance with the ferromagnetism theory as the degree of atomic thermal vibration increases; Above Curie temperature, the unique variety of coercivity is attributable to not only the competition between the 2nd and 4th order crystal field terms derived from the d electrons of Fe ³⁺ and Co ²⁺ in crystal cell, but also the easy magnetized direction switches from basal plane to c axis via a preferred orientation of the magnetic moments in microtubes structure; The high H _c value of CZF-microtube above Blocking temperature T _B (450.19 K) results from the existence of interparticle interaction as nanoparticles of it aggregate to produce a microtube structure, and resulting in a deviation from normal Kneller’s law.