Threads executing an operation a second

I'm trying to create a concurrent code where I execute a function per second, this function prints a character and waits a second on that thread. The behaviour I expect is to print each character after another but this doesn't happen, instead, it prints all of the characters of the inner loop execution. I'm not sure if this is somewhat related to an I/O operation or whatnot.

I've also tried to create an array of threads where each thread are created on the execution of the inner loop but the behaviour repeats, even if not calling join(). What might be wrong with the code?

The following code is what I've tried to do, and I used a clock to see if it was waiting the correct amount of time

#include <iostream>
#include <thread>
#include <chrono>
#include <string>

void print_char();

int main() {

    using Timer = std::chrono::high_resolution_clock;
    using te    = std::chrono::duration<double>;
    using s     = std::chrono::seconds;

    te interval;

    for (int i = 0; i < 100; i++) {
        auto  a = Timer::now();
        for (int j = 0; j < i; j++) {

            std::thread t(print_char);
            t.join();
        }
        auto b = Timer::now();
        interval = b-a;

        std::cout << std::chrono::duration_cast<s>(interval).count();
        std::cout << std::endl;
    }

        return 0;
}

void print_char() {
    std::cout << "*";
    std::this_thread::sleep_for(std::chrono::seconds(1));
}