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A ferrimagnetic hexagonal Ising nanotube with spin-1/2 core and spin-5/2 shell is investigated using the mean field approximation (MFA) and the Monte Carlo simulation (MCS). More exactly, we have examined the effects of the exchange interactions and crystal field on the magnetic properties of the system. Our phase diagrams show the appearance of critical and compensation behaviors, as well as first-order phase transitions terminating at isolated critical end-points in the ferrimagnetic phase region at low temperatures. Furthermore, we have made a comparison with other studies of similar nanosystems. [ABSTRACT FROM AUTHOR]

We investigated a three-dimensional semi-infinite spin-1/2 system bounded by a spin-1 surface using a Monte Carlo simulation based on the Metropolis algorithm. The exchange interactions and crystal field effects on phase diagrams, magnetizations, and susceptibilities were investigated. The phase diagrams in three planes were presented due to the competition between specific system parameters. The system demonstrated ordinary, extraordinary, surface, and special second-order phase transitions, as well as a surface first-order phase transition. Furthermore, tricritical and critical end-points were discovered. [ABSTRACT FROM AUTHOR]