Using a SQUID magnetometer, the magnetic field-induced magnetization was measured on a ferroelastically 'poled' orthorhombic ferroelec./ferroelastic single domain of Ni3B7O13Br. Measurements were performed along the three principal orthorhombic crystallog. axis directions at 0.5, 1.0, 3.0, and 5.0 kOe in the range 4-40 K, and at 10 kOe in the range 4-300 K. The corresponding magnetic susceptibilities were derived. The sequence of magnetic phases at low temp., their magnetic point groups and transition temps. Tcl = 30 K and Tc2 = 21 K were confirmed: mm21' <= Tc1 => m'm2' <= Tc2 +> 1. In the weakly ferromagnetic/ferroelec./ferroelastic orthorhombic phase with Shubnikov-Heesch point group m'm2' in the range 21 K < T < 30 K, the spontaneous magnetization vector Ms lies along the orthorhombic bo-axis, with a value of Ms = 0.71 emu/g at 25 K. In the triclinic phase with point Group 1, below Tc2 = 21 K, Ms assumes a temp.-dependent crystallog. general direction lying nearly in the pseudo-orthorhombic (001)0-plane, for example at 5 K with a value of Ms = (2.7a0 + 1.76b0 + 0.34c0) emu/g. [on SciFinder(R)]