2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/180677Contractions of Leibniz algebras and Courant algebroids by means of (1,1)-tensors are introduced and studied. An appropriate version of Nijenhuis tensors leads to natural deformations of Dirac structures and Lie bialgebroids. One recovers presymplectic-Nijenhuis structures, Poisson-Nijenhuis structures, and triangular Lie bialgebroids as particular examples.13 pages, to appear in J. Phys. A. A name of a font (which was wrongly interpreted by LaTeX in arXiv) has been changedDifferential GeometryMathematical Physics17B99; 17B62; 53C15; 53D17text