Magnetic acicular alloy particles containing iron as a main component according to the present invention, have an average major axial diameter of 0.05 to 0.2 .mu.m, and pH values of water suspensions of said magnetic acicular alloy particles containing iron as a main component, which satisfies the formula: (pH value of water suspension treated by A method)-(pH value of water suspension treated by B method)<0 Such magnetic acicular alloy particles containing iron as a main component exhibit an excellent dispersibility in a vehicle, especially such a vehicle composed of a binder resin having a polar group such as --SO.sub.3 M (wherein M is H, Na or K), --COOH or the like, and in which an orientation and a packing density in coating film are improved.

Las partículas acicular magnéticas de la aleación que contienen el hierro como componente principal según la actual invención, tienen un diámetro axial importante medio de 0.05 a 0.2 mu.m, y valores de pH de las suspensiones de agua de las partículas acicular magnéticas dichas de la aleación que contienen el hierro como componente principal, que satisface el fórmula: (el valor de pH de la suspensión de agua trató por el valor del method)-(pH de A de la suspensión de agua tratado por el método de B)