Room temperature ferromagnetism in HfO2 films

Abstract

HfO2 films were produced by sputter deposition in the substrate temperature (Ts) range of room temperature (RT)−300 °C and their structural, magnetic, and electrical properties were evaluated. The results indicate that the HfO2 films crystallize in the monoclinic structure and are oriented along the (−111) direction. Magnetization measurements (300–1.8 K) evidence their RT ferromagnetism. The effect of Ts is significant on the magnetic moment (M) and coercivity (Hc). M and Hc values enhanced with increasing Ts due to formation of oxygen vacancies. Increase in the temperature from 150 to 300 K decreases Hc without any transition, indicating that the Curie temperature of HfO2 films is higher than RT. Electrical measurements indicate that the HfO2 films are semiconducting.

Electronic and magnetic properties of the cation vacancy defect inm−HfO2

“…In a previous theoretical study we showed how the activation energy for small hole polaron diffusion in m-HfO 2 is rather low, 0.14 eV, consistent with the high temperature conductivity observations [51]. There has also been some speculation on the possible role cation vacancies may play in explaining observed ferromagnetism [31][32][33]35]. However, DFT calculations for m-HfO 2 employing local or semilocal functionals found relatively weak ferromagnetic coupling between cation vacancies insufficient to explain experimental observations [34,52].…”

“…One such example is provided by hafnium dioxide (HfO 2 ), a material which finds a number of applications in microelectronics [26,27]. It has been suggested that cation vacancies can induce high temperature p-type conductivity [28][29][30] and contribute to the so far unexplained ferromagnetism in HfO 2 [31][32][33][34][35]. However, our knowledge of the fundamental electronic and magnetic properties of cation vacancies in HfO 2 remains extremely limited, presenting an obstacle to deeper understanding of these complex effects.…”

Hybrids of Pd Nanoparticles and Metal–Organic Frameworks for Enhanced Magnetism

“…The crossing point of the ZFC and FC curves in UiO-66­(Hf) can be observed at approximately 270 K, above which the paramagnetic behavior is dominant. The existence of d 0 ferromagnetism in HfO 2 thin films has been reported by several authors. ,, In the case of UiO-66­(Hf), the source of magnetism can also be Hf 4+ with oxygen vacancies. However, ferromagnetic behavior in UiO-66­(Hf) has been observed only at low temperatures.…”

“…The existence of d 0 ferromagnetism in HfO 2 thin films has been reported by several authors. 32 , 44 , 45 In the case of UiO-66(Hf), the source of magnetism can also be Hf 4+ with oxygen vacancies. However, ferromagnetic behavior in UiO-66(Hf) has been observed only at low temperatures.…”

Hafnium oxide passivation of InGaAs/InP heterostructure bipolar transistors by electron beam evaporation

“…These dielectrics have extensively been investigated and are being used as gate oxides in scaled complementary metal oxide semiconductor (CMOS) and storage capacitors of dynamic random access memory (DRAM) devices [8][9][10]. Moreover, due to their outstanding electronic, optical and mechanical properties, high dielectric constant, and wide bandgap, HfO 2 based materials are also being actively investigated in several other industrial applications [11][12][13]. Nevertheless, beside few demonstrations of inversion mode III-V metal oxide semiconductor field effect transistors (MOSFETs) [14][15][16], there is a lack of information on the integration and potential use of the high-K-based dielectrics in III-V based electronic and optoelectronic components.…”