The propagation characteristics of an azimuthally magnetized solid-plasma circular guide are studied analytically and numerically. Families of design curves for millimeter control components, employing the nonreciprocal phase shifting and magnetically dependent cutoff, experienced by the higher-order TMo1 mode are presented: The structure capability to support backward wave propagation for the TMo1 mode and given direction of DC magnetic bias is explored and interpreted. The potentialities of the guide as device geometry for filters, traveling wave amplifiers and oscillators for millimeter frequencies are discussed.