No, the spin direction of a quantum entangled particle cannot be changed by manipulating the spin direction of its entangled counterpart, even if a strong external field is applied. This is because quantum entanglement is a phenomenon in which the quantum states of two or more particles become correlated in such a way that the states of the particles are interdependent.
When particles are entangled, their properties, such as spin, become linked in a way that the state of one particle is instantaneously connected to the state of the other, regardless of the physical distance between them. This connection persists even if the entangled particles are separated by vast distances.
According to the principles of quantum mechanics, the spin of an entangled particle is intrinsically uncertain until it is measured. When one particle's spin is measured, its corresponding entangled particle's spin becomes correlated, instantaneously "collapsing" into a definite state. This correlation holds regardless of any external fields or influences.
Therefore, while the spin direction of an entangled particle can be determined by measuring its spin, the act of measuring the spin of its entangled counterpart will not affect or change its own spin direction. The relationship between entangled particles remains independent of any external influences or measurements on one of the particles.