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Observations of lamellar like fringes in iron-carbon-filled vertically aligned carbon nanotubes (CNTs) produced by pyrolysis of ferrocene and rapid cooling methodologies (controlled quenching) have been investigated. The quantitative phase analysis of encapsulated Fe3C, γ-Fe, and α-Fe by X-ray diffraction reveals that controlling the phase-percentage leads to control of the crystal habit and of magnetic properties. Large coercivities and variable saturation magnetizations were observed. In addition, we reported a thorough study of the hysteresis behavior, the Barkhausen effect which has to be possibly associated with the formation of interfacial-defects in the crystal areas in contact with CNT layers. [ABSTRACT FROM AUTHOR]