NOVELTY - A rare earth permanent magnet contains alloy composition comprising substituted metal compound (I), where the rare earth permanent magnet is obtainable by absorption of fluoride of terbium and/or dysprosium through the surface of a sintered magnet body prepared from a mother alloy containing neodymium and praseodymium, or by absorption of terbium fluoride through the surface of a sintered magnet body prepared from the mother alloy, and the rare earth permanent magnet is in a form of a sintered magnet body having a center and a surface.    USE - Rare earth permanent magnet. Uses include but are not limited to household appliance, industrial equipment, electric automobile and wind power generator.    ADVANTAGE - The rare earth permanent magnet has better magnetic properties, and improved performance such as residual magnetic flux density and coercive force.    DETAILED DESCRIPTION - A rare earth permanent magnet contains alloy composition comprising substituted metal compound of formula (R1aR2bTcAdFeOfMg) (I), where the rare earth permanent magnet is obtainable by absorption of fluoride of terbium and/or dysprosium through the surface of a sintered magnet body prepared from a mother alloy containing neodymium and praseodymium, or by absorption of terbium fluoride through the surface of a sintered magnet body prepared from the mother alloy, the rare earth permanent magnet is in a form of a sintered magnet body having a center and a surface, constituent elements F and R2 are distributed such that their concentration increases on average from the center toward the surface of the magnet body, grain boundaries surround primary phase grains of (R1,R2)2T14A tetragonal system within the sintered magnet body, the R2 concentration (R2/(R1+R2)) contained in the grain boundaries is higher than the R2 concentration (R2/(R1+R2)) contained in the primary phase grains, and the oxyfluoride of (R1,R2) is present at grain boundaries in a grain boundary region that extends from the magnet body surface to a depth of 20 mu m or more.    R1=element chosen from rare earth elements, scandium and yttrium, but not including terbium or dysprosium, preferably 10 atom% of neodymium and/or praseodymium;    R2=terbium or dysprosium;    T=iron or cobalt, preferably 60 atom% of iron;    A=boron or carbon, preferably 80 atom% of boron;    F=fluorine;    M=aluminum, copper, zinc, indium, silicon, phosphorus, sulfur, titanium, vanadium, chromium, manganese, nickel, gallium, germanium, zirconium, niobium, molybdenum, palladium, silver, cadmium, tin, antimony, hafnium, tantalum or tungsten;    a+b=10-15;    d=3-15    e=0.01-4;    f=0.04-4;and    g=0.01-11, and the balance is c.    An INDEPENDENT CLAIM is also included for a method for preparing a rare earth permanent magnet in a form of a sintered magnet body, comprising the alloy composition.