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Recent work has shown that a young, rapidly rotating neutron star losesangular momentum to gravitational waves generated by unstable r-modeoscillations. We study the spin evolution of a young, magnetic neutron starincluding both the effects of gravitational radiation and magnetic braking(modeled as magnetic dipole radiation). Our phenomenological description ofnonlinear r-modes is similar to, but distinct from, that of Owen et al. (1998)in that our treatment is consistent with the principle of adiabatic invariancein the limit when direct driving and damping of the mode are absent. We showthat, while magnetic braking tends to increase the r-mode amplitude by spinningdown the neutron star, it nevertheless reduces the efficiency of gravitationalwave emission from the star. For B >= 10^14 (\nus/300 Hz)^2 G, where \nus isthe spin frequency, the spindown rate and the gravitational waveforms aresignificantly modified by the effect of magnetic braking. We also estimate thegrowth rate of the r-mode due to electromagnetic (fast magnetosonic) waveemission and due to Alfven wave emission in the neutron star magnetosphere. TheAlfven wave driving of the r-mode becomes more important than the gravitationalradiation driving when B >= 10^13 (\nus/150 Hz)^3 G; the electromagnetic wavedriving of the r-mode is much weaker. Finally, we study the properties of localRossby-Alfven waves inside the neutron star and show that the fractional changeof the r-mode frequency due to the magnetic field is of order 0.5 (B/10^16 G)^2(\nus/100 Hz)^-2.Comment: 18 pages, 4 figures; ApJ, accepted (v544: Nov 20, 2000); added two  footnotes and more discussion of mode driving by Alfven wave

r‐Mode Oscillations and Spin‐down of Young Rotating Magnetic Neutron Stars