A spin cluster glass behavior and a complicated exchange bias effect are observed in high quality BiFeO(3) nanocrystals grown by a hydrothermal method. The dynamic properties of the spin clusters investigated by measuring the frequency dependences of ac susceptibility show that the relaxation process can be described using a power law with the glass transition temperature T(g) = 57 K, relaxation time constant τ(0) = 4.4 × 10(-10) s, and critical exponent zv = 10.3 ± 1.9, consistent with a three-dimensional Ising spin glass. The exchange bias field (H(EB)) varies non-monotonically with temperature and achieves a minimum at T(g). The abnormal shift of hysteresis loops above T(g) may be interpreted in terms of a Malozemoff's random-field model with a framework of antiferromagnetic core/spin-cluster shell structure and a two-dimensional diluted antiferromagnet in a field (2D-DAFF) model, respectively. The exchange anisotropy of the BiFeO(3) nanocrystals will shed light on a possible application for magnetism related nanosized devices.

A large anisotropic remnant magnetization tunability was observed in multiferroic (011)-La_2/3Sr_1/3MnO₃/0.7Pb(Mg_2/3Nb_1/3)O₃-0.3PbTiO₃ (LSMO/PMN-0.3PT) epitaxial heterostructures. The remnant magnetization along [100] direction was suppressed by an electric field applied to the substrate while the remnant magnetization along $[01\overline{1}]$ was enhanced. The tunabilities of the remnant magnetization along the [100] and $[01\overline{1}]$ directions are about −17.9% and +157% under electric field of +7.27 kV/cm, respectively. This large anisotropic remnant magnetization tunability may find potential applications in the electrically written and magnetically read memories.

The ferroelectric and tunnel electro- and magnetoresistance properties in La_0.6Sr_0.4MnO₃/BiFeO₃/La_0.6Sr_0.4MnO₃ multiferroic tunnel junctions sandwiched with the antiferromagnetic-ferroelectric BiFeO₃ as a tunnel barrier were reported. Besides the four non-volatile resistance states and the interfacial magnetoelectric coupling effect with the tunnel magnetoresistance manipulated by ferroelectric polarizations, one of the most important results is that the exchange bias effect on the tunnel magnetoresistance is observed in this junction due to the magnetic interaction between antiferromagnetic BiFeO₃ and ferromagnetic La_0.6Sr_0.4MnO₃ layers. These finds may be helpful for designing exchange bias based multiferroic tunnel junction in next generation random access memory devices.

The non-volatile resistance states induced by converse piezoelectric effect are observed in ferromagnetic/ferroelectric epitaxial heterostructures of (011)-La_2/3Sr_1/3MnO₃/0.7Pb(Mg_2/3Nb_1/3)O₃-0.3PbTiO₃ (LSMO/PMN_0.7PT_0.3). Three stable remnant strain states and the corresponding resistance states are achieved by properly reversing the electric field from the depolarized direction in ferroelectric PMN_0.7PT_0.3 substrate. The non-volatile resistance states of the LSMO film can be manipulated by applied electric-field pulse sequence as a result of the large coupling between the electronic states of LSMO film and the strain transferred from the ferroelectric substrate. The electrically tunable, non-volatile resistance states observed exhibit potential for applications in low-power-consumption electronic devices.