The font is a variant/clone of Charter.
\documentclass[a4paper]{article}
\usepackage{geometry}
\usepackage{amsmath}
\usepackage{XCharter}
\usepackage[xcharter]{newtxmath}
\begin{document}
Although the electronic and magnetic transitions in the orthorhombic rare-earth
nickelates show relatively large responses in the resistivity and susceptibility
measurements, identifying the order parameters and the microscopic mechanism
behind these transitions has remained challenging. The metal-insulator and
paramagnetic-antiferromagnetic transitions in these materials
\[
a+b=\int_0^1 f(x)\,dx+\frac{\partial f}{\partial z}
\]
\end{document}

You can also use the not so different Utopia, or clone thereof, for instance loading fourier that perhaps has better covering for math.
\documentclass[a4paper]{article}
\usepackage{geometry}
\usepackage{amsmath}
\usepackage{fourier}
\begin{document}
Although the electronic and magnetic transitions in the orthorhombic rare-earth
nickelates show relatively large responses in the resistivity and susceptibility
measurements, identifying the order parameters and the microscopic mechanism
behind these transitions has remained challenging. The metal-insulator and
paramagnetic-antiferromagnetic transitions in these materials
\[
a+b=\int_0^1 f(x)\,dx+\frac{\partial f}{\partial z}
\]
\end{document}

With XeLaTeX or LuaLaTeX you can use Erewhon:
\documentclass[a4paper]{article}
\usepackage{geometry}
\usepackage{amsmath}
\usepackage{unicode-math}
\setmainfont{erewhon}
\setmathfont{Erewhon Math}
\begin{document}
Although the electronic and magnetic transitions in the orthorhombic rare-earth
nickelates show relatively large responses in the resistivity and susceptibility
measurements, identifying the order parameters and the microscopic mechanism
behind these transitions has remained challenging. The metal-insulator and
paramagnetic-antiferromagnetic transitions in these materials
\[
a+b=\int_0^1 f(x)\,dx+\frac{\partial f}{\partial z}
\]
\end{document}
