Temperature dependence of the domain structure in Fe14Nd2B single crystals during the spin-reorientation transition

The temperature dependence of the magnetic domain structure of Fe14Nd2B single crystals is investigated from room temperature down to 4.2K by means of the magneto-optical Kerr effect. The parallel stripe domain structure characteristic of high-anisotropy uniaxial ferromagnets is observed on the (h k 0) planes of the crystals at room temperature. This structure remains practically unchanged down to about 140 K. In the vicinity of the magnetic phase transition at T-SR = 135 K the domain structure undergoes intense realignment. Below T-SR a new type of domain structure occurs being characterized by a periodic modulation of the magnetization orientation inside the main domains together with a developed system of closure domains having different preferential orientations. For the particular sample studied the width of the main domains at 4.2 K is about 100 mu m, while that of closure domains is about 2-5 mu m.