provided for applying a magnetic field to the ferromagnetic fluid and the y junction in a direction normal to a plane defined by said y junction a composition processor is provided for dynamically changing a composition of the ferromagnetic fluid in response to a control signal to vary the permittivity and permeability of the ferromagnetic fluid application_number US 33076102 A description fig1 is a perspective view of a circulator 100 that is useful for understanding the invention for convenience the term circulator as used herein should also be understood to also include isolators which are really a special case of a circulator as illustrated in fig1 the circulator is comprised of metal case 116 and three transmission line ports 101 102 103 that are terminated in a y junction 104 electric ground planes 108 110 are shown above and below the transmission line ports 101 102 and 103 referring now to fig2 it can be seen that the circulator includes several components within the metal case 116 in conventional circulators ferrite discs are positioned in the area between the transmission line y junction 104 and the electric ground planes 108 110 in the present invention however the ferrite discs are preferably eliminated in favor of ferromagnetic fluid 114 that is contained within cylindrical cavity structures 113 115 magnets 112 are preferably provided above and below electric ground planes 108 and 110 respectively these can be either permanent magnets or electromagnets the metal case 116 is preferably formed of steel or aluminum with steel cladding to provide a magnetic return circuit.