RESUMO
From the viewpoints of large capacity, long-term guarantee, and low cost, interest in magnetic recording tapes has undergone a revival as an archive storage media for big data. Herein, we prepared a new series of metal-substituted ϵ-Fe2 O3 , ϵ-Ga(III) 0.31 Ti(IV) 0.05 Co(II) 0.05 Fe(III) 1.59 O3 , nanoparticles with an average size of 18â nm. Ga, Ti, and Co cations tune the magnetic properties of ϵ-Fe2 O3 to the specifications demanded for a magnetic recording tape. The coercive field was tuned to 2.7â kOe by introduction of single-ion anisotropy on Co(II) (S=3/2) along the c-axis. The saturation magnetization was increased by 44 % with Ga(III) (S=0) and Ti(IV) (S=0) substitution through the enhancement of positive sublattice magnetizations. The magnetic tape media was fabricated using an actual production line and showed a very sharp signal response and a remarkably high signal-to-noise ratio compared to the currently used magnetic tape.
RESUMO
Magnetic ferrites such as Fe(3)O(4) and Fe(2)O(3) are extensively used in a range of applications because they are inexpensive and chemically stable. Here we show that rhodium-substituted ε-Fe(2)O(3), ε-Rh(x)Fe(2-x)O(3) nanomagnets prepared by a nanoscale chemical synthesis using mesoporous silica as a template, exhibit a huge coercive field (H(c)) of 27 kOe at room temperature. Furthermore, a crystallographically oriented sample recorded an H(c) value of 31 kOe, which is the largest value among metal-oxide-based magnets and is comparable to those of rare-earth magnets. In addition, ε-Rh(x)Fe(2-x)O(3) shows high frequency millimetre wave absorption up to 209 GHz. ε-Rh(0.14)Fe(1.86)O(3) exhibits a rotation of the polarization plane of the propagated millimetre wave at 220 GHz, which is one of the promising carrier frequencies (the window of air) for millimetre wave wireless communications.